On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

Z: Intermittent

Z1 DIRECTION FOR INTERMITTENT DIAGNOSTIC PATH

There are two main procedures used in this section to isolate and repair an intermittent concern. One will utilize the Rotunda Distributorless Ignition System Tester (DIST) and the other, a scan tool with digital multimeter.
The DIST is available for use on vehicles with coil pack ignition systems.

Is this a predetermined ignition concern on a coil pack application?

Yes	No
GO to Z50 .	GO to Z2 .

Z2 PERFORM PCM RESET TO CLEAR FMEM

Note: Proceed with this step only if a PCM Reset was not done earlier; otherwise, proceed with GO to Z3 . Eliminating FMEM will insure reproduction of any PCM related symptom.

Connect scan tool to Data Link Connector (DLC).
Key on, engine off.

Note: Be sure freeze frame data has been recorded before resetting the PCM.

Complete a PCM reset.

Is the PCM Reset complete?

Yes	No
GO to Z3 .	Complete PCM Reset. GO to Z3 .

Z3 SELECT PIDS RELATED TO THE SYMPTOM

A list of PIDs is needed for use with the scan tool to indicate the area of fault. Obtain the customer symptom description. Use the Reference Value Symptom Chart and proceed to the Reference Value PID/Measurement Signal Chart. These are located in the beginning of Section 6 , Reference Values.
Highlight each PID recommended by the charts under the PID selection menu on the scan tool.

Have all PIDs related to the symptom been chosen?

Yes	No
GO to Z4 .	REPEAT Z3 .

Z4 DECISION TO VERIFY SYMPTOM

The path to symptom verification is optional, but is recommended for several reasons; some are because:

Vehicle is in for repeat repair.
No DTC is present.
Customer has difficulty describing the symptom.

Does symptom need to be verified?

Yes	No
GO to Z5 .	GO to Z11 .

Z5 COLLECT ANY AVAILABLE DATA TO AID IN SYMPTOM VERIFICATION

Note: Only MIL codes will trigger freeze frame data. Refer to scan tool instruction manual to retrieve freeze frame information.

Prepare freeze frame data for use which was recorded earlier from the Symptom Charts in Section 3 .
Continuous Memory DTCs should already be recorded from an earlier pinpoint test.
Access information from the customer worksheet or any other available data from the customer.

Has all data been recorded?

Yes	No
GO to Z6 .	GATHER as much data as possible to aid in isolation of the intermittent fault area. REPEAT Z5 .

Z6 RECREATE SYMPTOM USING ALL DATA

Note: Vehicle may require some driving to proceed with this test step. The concern must be verified by recreating the conditions that originally set the DTC.

With the scan tool, select and monitor the same PIDs as displayed in freeze frame along with the previous highlighted PIDs from Step Z3 . Using freeze frame data recorded earlier, recreate the conditions described by each freeze frame PID. Pay special attention to ECT, LOAD, RPM and VSS. Also, use any available customer data to aid in producing the correct conditions for recreating the symptom.
When the symptom occurs, press trigger to begin recording (Refer to the scan tool instruction manual for recorder function).

Could symptom be reproduced?

Yes	No
GO to Z11 .	GO to Z7 .

Z7 RECREATE SYMPTOM USING KOEO ROAD TEST PROCEDURE

The road test is the last attempt to locate the area of concern before physically disturbing vehicle circuits.

Note: PIDs for outputs in the Reference Value Charts represent commanded values only. Circuit measurements with digital multimeter indicate actual output status. Therefore, in the case of a fault, the PID and circuit reading on the vehicle may not correspond with each other. PIDs for PCM inputs with a mismatch to the circuit measurement indicate a possible PCM concern.

The Intermittent Road Test Procedure is a set of instructions for monitoring PIDs with a scan tool of circuit measurements with a digital multimeter. This is done under four different conditions - KOEO, HOT IDLE, 48 and 88 kmh (30 and 55 mph). Use the Typical Diagnostic Reference Values from Section 6 , Reference Values to compare with the actual vehicle values. For 48 and 88 kmh (30 and 55 mph) procedures, a planned route with passenger is required.
Locate the corresponding Reference Value chart in Section 6 .
Set vehicle up to measure circuits with a digital multimeter and scan tool.
Connect scan tool to DLC.
Key on, engine off.
With the scan tool, select and monitor PIDs and also measure circuits shown in the Reference Value Chart in Section 6 .
Compare the scan tool PIDs and digital multimeter values to the Reference Value Charts.

Are any values out of range?

Yes	No
GO to Z11 .	GO to Z8 .

Z8 RECREATE SYMPTOM USING HOT IDLE ROAD TEST PROCEDURE

Key on, engine running and at least 87°C (195° F).
Continue to monitor the same PIDs and circuits as in the previous step at hot idle.

Are any values out of range?

Yes	No
GO to Z11 .	GO to Z9 .

Z9 RECREATE SYMPTOM USING 48 KMH (30 MPH) SLOW CRUISE ROAD TEST PROCEDURE

Drive vehicle on preplanned route.
Continue to monitor the same PIDs and circuits during slow cruise as in the previous step.

Are any values out of range?

Yes	No
GO to Z11 .	GO to Z10 .

Z10 RECREATE SYMPTOM USING 88 KMH (55 MPH) HIGH CRUISE ROAD TEST PROCEDURE

Continue to drive vehicle on preplanned route.
Continue to monitor the same PIDs and circuits during high cruise as in the previous step.

Are any values out of range?

Yes	No
GO to Z11 .	It is now necessary to physically disturb selected vehicle circuits in an attempt to recreate the intermittent concern. GO to Z11 .

Z11 SELECT CIRCUITS FROM THE INTERMITTENT TEST CHART

Remain in the PID selection menu with the scan tool.
If the Intermittent Road Test was used to verify the symptom, highlight PIDs or signals that displayed a mismatch to the Reference Values from Section 6 . Otherwise, highlight only the PIDs from Step Z3 .
Proceed to the Intermittent Test Chart located at the beginning of this pinpoint test.
Match selected PIDs to the corresponding circuit in the chart. There may be more than one circuit to test. If a PID recording was made with the scan tool, it may be helpful to replay at this time (refer to the scan tool instruction manual for recorder function).
From the same chart, select and proceed to the appropriate test:

Input Test - Used on sensing devices such as temperature, position or oxygen.
Output Test - Used on output devices such as relays, coils or solenoids.

Has a test been chosen?

Yes	No
For Input Test : GO to Z12 . For Output Test : GO to Z16 .	To diagnose other driveability symptoms, GO to Section 3 , Symptom Charts.

Z12 KOEO INPUT TEST PROCEDURE FOR PCM SENSORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS, OR HOT SURFACES.

Using circuits chosen from the Intermittent Test Chart, select only the recommended PID(s) to monitor with the scan tool. If a PID is not available for the circuit, use a digital multimeter.
Proceed to the area of the suspect wiring or component fault.
Key on, engine off.
If the input is a switch-type component, turn on manually.
Monitor the PID or digital multimeter values while tapping on component.
Monitor while wiggling sensor harness wire from component to PCM.
Look for abrupt changes in values. Compare the actual values to the KOEO Typical Diagnostic Reference Values in Section 6 , Reference Values.

Are values fluctuating in and out of range?

Yes	No
REPAIR as necessary.	GO to Z13 .

Z13 KOER INPUT TEST PROCEDURE FOR PCM SENSORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS, ENGINE DRIVE BELTS OR HOT SURFACES.

Key on, engine running.
Continue to monitor PIDs or circuits as in Step Z12 .
Proceed to the area of the suspect wiring or component fault.
If the input is a switch-type component, turn on manually.
Monitor the PID or digital multimeter values while tapping on component.
Monitor while wiggling sensor harness wire from component to PCM.
Look for abrupt changes in values. Compare the actual values to the HOT IDLE Typical Diagnostic Reference Values in Section 6 , Reference Values.

Are any values fluctuating in and out of range?

Yes	No
REPAIR as necessary.	GO to Z14 .

Z14 KOEO WATER SOAK TEST PROCEDURE FOR PCM SENSORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS OR HOT SURFACES.

Key on, engine off.
Continue to monitor PIDs or circuits scan tool as in Step Z13 .
Proceed to the area of the suspect wiring or component fault.
If the input is a switch-type component, turn on manually.
Monitor the PID or digital multimeter values while lightly spraying a water mist on the component.
Monitor while spraying sensor harness wire from component to PCM.
Look for abrupt changes in values. Compare the actual values to the KOEO Typical Diagnostic Reference Values in Section 6 , Reference Values.

Are any values fluctuating in and out of range?

Yes	No
REPAIR as necessary.	GO to Z15 .

Z15 KOER WATER SOAK TEST PROCEDURE FOR PCM SENSORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS, ENGINE DRIVE BELTS OR HOT SURFACES.

Key on, engine running.
Continue to monitor PIDs or circuits scan tool as in Step Z14 .
Proceed to the area of the suspect wiring or component fault.
If the input is a switch-type component, turn on manually.
Monitor the PID or digital multimeter values while lightly spraying a water mist on the component.
Monitor while spraying sensor harness wire from component to PCM.
Look for abrupt changes in values. Compare the actual values to the KOEO Typical Diagnostic Reference Values in Section 6 , Reference Values.

Are values fluctuating in and out of range?

Yes	No
REPAIR as necessary.	GO to Z16 .

Z16 KOEO OUTPUT TEST PROCEDURE FOR PCM ACTUATORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS OR HOT SURFACES.

Note: PIDs selected from the Intermittent Test Chart will display commanded values only. Digital multimeter measurements will display actual values.

Using circuits chosen from the Intermittent Test Chart, select the recommended PID(s) to monitor using the scan tool. Also, use a digital multimeter to compare circuit values with the scan tool PID values. If PIDs are not available for a particular circuit, look for a digital multimeter fluctuation to occur when doing any of the following tests.

Note: Output Test Mode may not control some outputs, such as injectors and ignition coils. To test these output types, go to Z17 . Caution must be used for the next steps. Cooling fans or fuel pump may turn on.

Key on, engine off.
With the scan tool, turn all outputs on using Output Test Mode (refer to scan tool instruction manual).
Proceed to the area of the suspect wiring or component fault.
Monitor the PID and digital multimeter values while tapping on component.
Monitor while wiggling actuator harness wire from component to PCM.
Look for abrupt changes or PID to digital multimeter value mismatches. Also, compare the actual values to the KOEO Typical Diagnostic Reference Values in Section 6 , Reference Values.

Is there a mismatch or are any values fluctuating in and out of range on the Reference Value Charts?

Yes	No
REPAIR as necessary.	GO to Z17 .

Z17 KOER OUTPUT TEST PROCEDURE FOR PCM ACTUATORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS, ENGINE DRIVE BELTS OR HOT SURFACES.

Key on, engine running.
Proceed to the area of the suspect wiring or component fault.
Monitor PIDs with the scan tool (if PIDs are available) using the PID monitor function. Compare the digital multimeter values with scan tool or look for a fluctuation in idle while tapping on the component.
If a coil for a coil on plug application has been tapped and is suspect, with key off, it may be helpful to remove the coil and measure continuity from the spark plug terminal to the signal terminal while tapping the coil. A large fluctuation in resistance will indicate an intermittent open. Otherwise, monitor while wiggling actuator harness wire from component to PCM.
Look for abrupt changes in idle or PID to digital multimeter value mismatches or fluctuation. Also, compare the actual values to the HOT IDLE Typical Diagnostic Reference Values in Section 6 , Reference Values.

Is there an idle fluctuation, a digital multimeter value mismatch or fluctuation?

Yes	No
REPAIR as necessary.	GO to Z18 .

Z18 KOEO WATER SOAK TEST PROCEDURE FOR PCM ACTUATORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS OR HOT SURFACES.

Note: Output Test Mode may not control some outputs, such as injectors. To test these output types, go to Z19 .

Key on, engine off.
With the scan tool, turn all outputs on using Output Test Mode (refer to scan tool instruction manual).
Proceed to the area of the suspect wiring or component fault.
Monitor the PID and digital multimeter value while spraying a light mist of water on the component.
Monitor while spraying actuator harness wire from component to PCM.
Look for abrupt changes or PID to digital multimeter value mismatches. Also, compare the actual values to the KOEO Typical Diagnostic Reference Values in Section 6 , Reference Values.

Is there a PID to digital multimeter value mismatch or fluctuation in and out of range according to the Reference Value Charts?

Yes	No
REPAIR as necessary.	GO to Z19 .

Z19 KOER WATER SOAK TEST PROCEDURE FOR PCM ACTUATORS

WARNING: WHEN PERFORMING ANY OF THE TEST STEPS, ALWAYS BE AWARE OF HANDS, CLOTHING OR TOOLS NEAR COOLING FANS, ENGINE DRIVE BELTS OR HOT SURFACES.

Key on, engine running.
Monitor PIDs with the scan tool using the PID monitor function and continue to compare with the digital multimeter.
Proceed to the area of the suspect wiring or component fault.
Monitor the PID and digital multimeter value while spraying water mist on the component.
Monitor while lightly spraying actuator harness wire from component to PCM.
Look for abrupt changes in idle or PID to digital multimeter value mismatches. Also, compare the actual values to the Hot Idle Typical Diagnostic Reference Values in Section 6 , Reference Values.

Is there an idle fluctuation, value mismatch or values fluctuating in and out of range according to the Reference Value Charts?

Yes	No
REPAIR as necessary.	KEY OFF. GO to Z20 .

Z20 INSPECT FOR INTERMITTENT MECHANICAL CONCERNS

Note: It is possible for an intermittent mechanical concern to cause a good PCM system to react abnormally.

An inspection of mechanical systems relating to the DTC or symptom should have been performed in an earlier section. If not, visually inspect at this time.
Look for the possibility of wires, vacuum lines or hoses that may short or kink during normal engine operation, such as:

Engine rock during acceleration.
Components moving during conditions of vibrations (high rpm or rough road).
Accelerator or transmission linkage contact or interference.

Is a mechanical concern detected?

Yes	No
REPAIR as necessary.	It is necessary to seek additional help. REFER to the OASIS system or Hotline. A customer flight recorder may also be useful.

Z50 INTERMITTENT IGNITION PROCEDURE

PRELIMINARY CHECKS

Note: This pinpoint test must be used with the Rotunda DIST Distributor/Less Ignition System Tester 418-F024 (007-00075) or equivalent for non coil on plug applications only. If this tester is not available, or this is a coil on plug application, return to Z2 and continue. Quick Test must be performed and instructions in Section 5 Pinpoint Test steps completed before starting the intermittent ignition procedure.

Check sensor shield connector.
Be certain the battery is fully charged.
All accessories must be off during diagnosis.

Is vehicle prepared for equipment set-up?

Yes	No
GO to Z51 .	REPEAT Z50 .

Z51 INSTALL DIST TESTER

All accessories must be off during testing.
Select proper Overlay and Program Cartridge to match the ignition system to be tested.
Install overlay on front panel of tester.
Insert Program Cartridge into the cartridge slot (marked on the RH side of the front panel). Make sure the cartridge is fully inserted.
Select and install the proper harness adapter to the Rotunda DIST Distributor/Less Ignition System Tester 104-Pin PCM Adapter 007-00110. Set the rotary knob to position I.
Verify that the WIGGLE TEST switch is in the OFF position. For 2.5L Ranger, verify that the SYSTEM TYPE switch is set to DUAL PLUG; all other four cylinders set to NON DUAL PLUG.
WIGGLE TEST can only be used during key on, engine off.

WIGGLE TEST monitors circuits for intermittent faults.
WIGGLE TEST MODES A, B, and C check for short to power, open, and short to ground respectively.
Simulate fault conditions by wiggling the wiring harness and tapping on connectors and components.
The DIST will beep and turn on the LED for the circuit on which a fault is detected.

Disconnect the vehicle wiring harness from PCM.
Hook Tester to PCM and vehicle wiring harness.
Key on, engine off. Press Tester RESET button. The tester performs Self-Test when it is reset or powered up. During the Self-Test, all LEDs will light and a beep will be heard.
If the CASE GND (CKP SHIELD) FAULT MEMORY LED (EI only) stays on, run a ground line from the PCM Case to GND and continue with test.

Does the tester perform Self-Test and is the VPWR LED on?

Yes	No
GO to Z220 .	KEY OFF. GO to tester check in Z52 .

Z52 TESTER CHECK

Disconnect tester from vehicle.
Connect a jumper wire from VPWR jack to vehicle battery POS (+) terminal.
Connect a jumper wire from PWR GND jack to vehicle battery NEG (-) terminal.
If tester performs Self-Test, reconnect tester to vehicle and Go to Z190 .
If tester does not perform Self-Test, refer to tester manual.
If LEDs do not light or beep is not heard during Self-Test, refer to tester manual.

Does tester pass Self-Test?

Yes	No
GO to Z220 .	DIST tester does not pass Self-Test. REFER to Warranty supplied with DIST tester.

Z190 CHECK VPWR CIRCUIT FOR OPEN

Key on, engine off.
Measure the voltage from VPWR jack to the battery GND(-) terminal.

Is the reading greater than 6 volts?

Yes	No
KEY OFF. GO to Z191 .	KEY OFF. REPAIR open in VPWR circuit harness to PCM. RETURN to Z51 .

Z191 CHECK PWR GND CIRCUIT FOR OPEN BETWEEN PCM AND B-

Measure the resistance between PWR GND jack and B-.

Is resistance less than 5 ohms?

Yes	No
GO to Z192 .	REPAIR open circuit. RETURN to Z51 .

Z192 WIGGLE TEST MODE B - POWER CIRCUIT

Connect a jumper wire from PWR GND jack to the battery GND(-) terminal.
Key on, engine off.
WIGGLE TEST switch ON.
Place MODE switch to B.
Wiggle Test.

Does the tester reset?

Yes	No
KEY OFF. REPAIR open in VPWR circuit harness to PCM. RETURN to Z51 .	KEY OFF. REPAIR open in PWR GND circuit harness to PCM. RETURN to Z51 .

Z220 CHECK FOR COIL FAULTS

Press RESET button and wait for tester to initialize.

Are any COIL FAULT MEMORY LEDs on or flashing?

Yes	No
GO to Z229 .	GO to Z221 .

Z221 CHECK CASE GND/CKP SHIELD

Is the CASE GND/CKP SHD FAULT MEMORY LED on or flashing?

Yes	No
GO to Z253 .	GO to Z222 .

Z222 CKP BIAS CHECK

Is the CKP BIAS SYSTEM STATUS LED on?

Yes	No
GO to Z223 .	KEY OFF. GO to Z243 .

Z223 CHECK FOR COIL FAULT

With the DIST connected to the vehicle, try to recreate the fault by test driving the vehicle. If the vehicle is a No Start, crank engine for 5 to 10 seconds.

Are any COIL FAULT MEMORY LEDs on during crank or engine run?

Yes	No
KEY OFF. GO to Z229 .	GO to Z224 .

Z224 CASE GND/CKP SHIELD FAULT

Key on, engine running or key on, engine cranking as described in Z223 .

Is the CASE GND/CKP SHIELD FAULT MEMORY LED on during crank or engine run?

Yes	No
KEY OFF. GO to Z253 .	GO to Z225 .

Z225 CHECK CKP STATUS

Key on, engine running or key on, engine cranking as described in Z223 .

Is the CKP SYSTEM STATUS SIGNAL LED on during crank or engine run?

Yes	No
GO to Z226 .	GO to Z247 .

Z226 CHECK FOR CTO FAULT

Key on, engine running or key on, engine cranking as described in Z223 .

Is the CTO FAULT MEMORY LED on during crank or engine run?

Yes	No
KEY OFF. GO to toZ239 .	GO to Z227 .

Z227 CHECK FOR CKP SIGNAL

Key on, engine running or key on, engine cranking as described in Z223 .

Is the CKP SIGNAL SYSTEM STATUS LED on during crank or engine run?

Yes	No
Fault is not related to ignition system. RETURN to Z1 .	KEY OFF. GO to Z247 .

Z229 CHECK COIL IGN START/RUN CIRCUIT FOR OPEN

Disconnect coil pack(s).
Key on, engine off.
Measure voltage from IGN Start/Run at coil pack connector(s) to PWR GND jack.

Is the voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to Z230 .	SERVICE VPWR harness(es) to coil pack(s). RETEST.

Z230 CHECK COIL DRIVER CIRCUITS FOR SHORT TO VPWR AND PWR GND

Measure resistance from COIL jacks to PWR GND jack.
Measure resistance from COIL jacks to VWPR jack.

Is any resistance less than 6K ohms?

Yes	No
GO to Z236 .	GO to Z231 .

Z231 CHECK COIL CIRCUIT FOR OPEN IN HARNESS

Measure resistance from each COIL jack to its pin in the coil harness connector.

Is each resistance less than 5 ohms?

Yes	No
GO to Z232 .	REPAIR coil harness. RETEST.

Z232 CHECK COIL LINES FOR SHORT TOGETHER

Measure resistance from every COIL jack to all other COIL jacks.

Is any resistance less than 10K ohms?

Yes	No
GO to Z237 .	GO to Z233 .

Z233 CHECK COIL CIRCUIT(S) FOR HARD FAULT

Reconnect coil pack(s).
Key on, engine off.
Press RESET button.
Wait for tester initialization.
Wait for coil test to run.

Are any COIL FAULT MEMORY LEDs on or flashing?

Yes	No
KEY OFF. GO to Z238 .	GO to Z234 .

Z234 WIGGLE TEST MODE B - COIL CIRCUIT(S)

Place WIGGLE TEST switch to ON.
Place MODE switch to B.
Press RESET button.
Wait for WIGGLE TEST ACTIVE LED to light.
Wiggle Test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED to light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	KEY OFF. GO to Z235 .

Z235 COIL DISCONNECTED WIGGLE TEST MODE B

Disconnect coil pack(s).
Key on, engine off.
Wait for WIGGLE TEST ACTIVE LED to light.
Wiggle test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z236 ISOLATE COIL LINE SHORTS FOR VPWR AND PWR GND

Disconnect PCM, leave DIST connected.
Measure resistance from each COIL jack to PWR GND jack.
Measure resistance from each COIL jack to VPWR jack.

Is any resistance less than 10K ohms?

Yes	No
REPAIR coil harness. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z237 ISOLATE COIL LINE SHORTS BETWEEN COILS

Disconnect PCM.
Reconnect DIST between coil harness.
Measure resistance from every COIL jack to all other COIL jacks.

Is any resistance less than 10K ohms?

Yes	No
REPAIR coil harness. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z238 CHECK FOR CORROSION

Check ignition system connectors for corrosion.

Is any corrosion present?

Yes	No
REPAIR connectors. RETEST.	REPLACE damaged coil pack(s). RETEST.

Z239 CHECK CTO CIRCUIT FOR SHORTS TO VPWR AND PWR GND

Measure resistance from CTO to VPWR jack.
Measure resistance from CTO to PWR GND jack.

Is any resistance less than 1K ohm?

Yes	No
GO to Z240 .	GO to Z241 .

Z240 ISOLATE CTO SHORTS

Disconnect PCM.
Reconnect DIST to harness.
Measure resistance from CTO to VPWR jack.
Measure resistance from CTO to PWR GND jack.

Is any resistance less than 1K ohm?

Yes	No
REPAIR CTO harness/tachometer. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z241 WIGGLE TEST MODE B - CTO CIRCUIT

Key on, engine off.
Place WIGGLE TEST switch to ON.
Place MODE switch to B.
Press RESET button.
Wait for WIGGLE TEST ACTIVE LED to light.
Wiggle test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED to light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	GO to Z242 .

Z242 WIGGLE TEST - CHECK FOR FAULT

6 or 4 cylinder: Set MODE switch to A.
8 cylinder: Set MODE switch to C.
Press RESET button.
Wait for WIGGLE TEST ACTIVE LED to light.
Wiggle Test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED to light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z243 CHECK CKP BIAS

Disconnect harness from CKP sensor.
Key on, engine off.
Press RESET button and wait for tester to initialize.

Is the CKP BIAS SYSTEM STATUS LED on?

Yes	No
KEY OFF. GO to Z245 .	KEY OFF. GO to Z244 .

Z244 ISOLATE SHORT TO VPWR AND PWR GND FOR CKP+ CIRCUIT

Disconnect PCM.
Reconnect DIST to harness.
Measure resistance from CKP+ jack to VPWR jack.
Measure resistance from CKP+ jack to PWR GND jack.

Are both resistances greater than 10K ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.	REPAIR CKP harness. RETEST.

Z245 CHECK CKP- CIRCUIT FOR SHORTS TO VPWR AND PWR GND

Measure resistance from CKP- jack to PWR GND jack.
Measure resistance from CKP- jack to VPWR jack.

Are both resistances greater than 10K ohms?

Yes	No
REPLACE CKP sensor. RETEST.	GO to Z246 .

Z246 ISOLATE SHORTS TO VPWR AND PWR GND FOR CKP- CIRCUIT

Disconnect PCM.
Reconnect DIST to harness.
Measure resistance from CKP- jack to PWR GND jack.
Measure resistance from CKP- jack to VPWR jack.

Are both resistances greater than 10K ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.	REPAIR CKP harness. RETEST.

Z247 CHECK FOR CKP SIGNAL

Press RESET button and wait for tester to initialize.
Crank or start engine.

Is the CKP SIGNAL SYSTEM STATUS LED on during crank or engine run?

Yes	No
GO to Z252 .	KEY OFF. GO to Z248 .

Z248 CHECK FOR CKP CIRCUIT RESISTANCE

Disconnect CKP sensor.
Measure resistance from CKP+ jack to CKP+ pin in harness sensor connector.
Measure resistance from CKP- jack to CKP- pin in harness sensor connector.

Are both resistances less than 5 ohms?

Yes	No
GO to Z249 .	REPAIR CKP harness. RETEST.

Z249 CHECK FOR CKP+ SHORT

Measure resistance from CKP+ jack to CKP- jack, PWR GND jack and VPWR jack.

Are all resistances greater than 10K ohms?

Yes	No
GO to Z251 .	GO to Z250 .

Z250 ISOLATE SHORT FOR CKP+

Disconnect PCM.
Reconnect DIST to harness.
Measure resistance from CKP+ jack to CKP- jack, PWR GND jack and VPWR jack.

Are all resistances greater than 10K ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.	REPAIR harness as needed. RETEST.

Z251 CHECK FOR PHYSICAL DAMAGE

Inspect CKP sensor and pulse wheel for misalignment, incorrect air gap and physical damage.

Are the sensor and data wheel OK?

Yes	No
REPLACE CKP sensor. RETEST.	REPAIR as needed. RETEST.

Z252 WIGGLE TEST - CKP CIRCUIT

Key on, engine off.
Place WIGGLE TEST switch to ON.
Place MODE switch to B.
Press RESET button.
Wait for WIGGLE TEST ACTIVATED LED to light.
Wiggle Test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED to light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.

Z253 CHECK CKP SHD FOR SHORT TO PWR

Measure resistance from CASE GND/CKP SHD jack to VPWR jack.

Is the resistance greater than 10K ohms?

Yes	No
GO to Z255 .	GO to Z254 .

Z254 ISOLATE SHORT FROM SHD TO PWR

Disconnect PCM.
Reconnect DIST to harness.
Measure resistance from CASE GND/CKP SHD jack to VPWR jack.

Is the resistance greater than 10K ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). RETEST.	REPAIR CASE GND/CKP SHIELD harness. RETEST.

Z255 WIGGLE TEST MODE B - CKP CIRCUIT

Key on, engine off.
Place WIGGLE TEST switch to ON.
Place MODE switch to B.
Press RESET button.
Wait for WIGGLE TEST ACTIVE LED to light.
Wiggle Test.

Are any FAULT MEMORY LEDs on?

Yes	No
PRESS RESET and WAIT for WIGGLE TEST ACTIVE LED to light. CONTINUE to test until intermittent is isolated. REPAIR as necessary. RETEST.	REPAIR CASE GND/CKP shield harness. RETEST.