On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

HU: Intake Air Systems

HU1 CHECK FOR INCORRECT IDLE SPEED

Note: Vehicle must be at operating temperature and at idle for a minimum of one minute. If here for a part throttle symptom, GO to HU4 .

Key on, engine running.
Determine if idle speed is incorrect. Refer to the Typical Reference Value Charts in Section 6 , if necessary.
Read the vehicle tachometer (if equipped) or connect the scan tool to the data link connector (DLC) and view the rpm PID.

Is vehicle idle speed incorrect?

Yes	No
For a high idle concern, be sure throttle arm contacts return stop, then GO to HU6 . For other idle speed concerns, GO to HU7 .	KEY OFF. GO to HU2 .

HU2 CHECK FOR STICKING/BINDING CONDITION

Gently cycle throttle from fully closed to fully open and back to fully closed. Check for binding/sticking in travel.

Is a stick or bind condition present?

Yes	No
GO to HU3 .	GO to HU4 .

HU3 ISOLATE BINDING/STICKING CONCERN

Disconnect accelerator cable and speed control cable from throttle body linkage.

CAUTION: Do not attempt to clean the throttle bore and plate area. Cleaning will damage the throttle body assembly.

Note: Sticking or binding condition can either be within cables or throttle body assembly.

Rotate throttle body linkage.

Does the throttle body rotate freely without a sticking, binding or grabbing condition?

Yes	No
REPAIR cable(s) causing the concern.	REPLACE throttle body assembly.

HU4 CHECK FUNCTIONALITY OF THE THROTTLE POSITION SENSOR

Key on.
View TP V PID with the scan tool.
From closed throttle, slowly begin to press accelerator to wide open throttle.

Did the TP V PID display a smooth reading during accelerator movement?

Yes	No
KEY OFF. GO to HU5 .	REPLACE throttle position sensor.

HU5 CHECK FOR AIR CLEANER ELEMENT AND INLET FOR RESTRICTIONS

Remove air cleaner element. Check for a plugged or dirty element.
Check for any restrictions along the air inlet path from the air inlet back to the throttle body.

Are any restrictions present?

Yes	No
REPAIR air cleaner element or clear any restrictions.	REINSERT original air cleaner element. GO to HU6 .

HU6 CHECK FOR A POSITIVE CRANK VENTILATION CONCERN

Note: A high idle may indicate incorrect PCV valve size or vacuum leak.

Inspect PCV valve connections for leaks or cracks.
Remove PCV valve and inspect for plugging or an incorrect valve.

Is a PCV concern present?

Yes	No
REPLACE PCV valve or REPAIR leak or crack.	For high idle, GO to HU9 , otherwise, RECONNECT PCV valve. GO to HU7 .

HU7 CHECK FOR IDLE AIR CONTROL VALVE RESPONSE

Key on, engine running.
With vehicle at operating temperature and at idle for a minimum of one minute, disconnect the IAC valve harness connector.

Did engine idle speed drop or nearly stall?

Yes	No
GO to HU8 .	For a high idle with no idle speed drop when disconnecting IAC, GO to HU9 . For a low idle with no idle speed drop when disconnecting IAC, REPLACE the IAC valve.

HU8 INSPECT THROTTLE BODY PLATE HOLE FOR PLUGGING

Note: Only some applications have a throttle plate hole. If not equipped, return to symptom charts.

Detach resonator from throttle body assembly.
Inspect throttle plate hole for any restrictions.

Is the throttle plate hole restricted?

Yes	No
CLEAR throttle plate hole.	Return to Symptom Charts.

HU9 CHECK FOR VACUUM LEAKS

Listen for vacuum leaks.
Inspect entire air intake system from the mass air flow (MAF) sensor to the intake manifold for leaks such as:

cracked or punctured inlet air tube.
loose connections on the inlet air tube at the air cleaner housing or throttle body.
idle air control (IAC) valve assembly or gasket seal.
EGR valve gasket seal leak to intake manifold.
Intake manifold assembly or gasket seal.
EGR valve diaphragm or control solenoid.
vacuum supply connectors and hose.

Are any leaks detected?

Yes	No
KEY OFF. REPAIR any leaks.	REPLACE IAC valve if idle speed does not drop when disconnecting harness connector otherwise, KEY OFF. GO to HU10 .

HU10 CHECK THROTTLE BODY FOR EXCESSIVE WEAR

Remove throttle body assembly (refer to Intake Air Distribution and Filtering, Section 303-12 in the Workshop Manual).
Hold throttle body up to a light source.
Rotate the throttle lever to wide open throttle and inspect bore for excessive wear or grooving.
Rotate the throttle lever to closed throttle position while inspecting for misaligned or worn plate. Look for excessive gap between bore and plate area.

Is a concern detected?

Yes	No
REPLACE throttle body.	RETURN to Symptom Charts.

HU15 DTCS P1516, P1517, P1518, P1519, P1520, P1537, P1538 PERFORM VISUAL INSPECTION

Note: Refer to the PCM connector pin numbers in the beginning of the pinpoint test.

View linkage or cable routing. Check for any binding or improper routing. Cable core wire (if applicable) at IMRC housing attachment must have slack and lever must contact close plate stop screw. For Escort/Tracer, view IMRC actuator lever. Make sure lever is visible. Refer to the IMRC system description in Section 1 , Intake Air and Throttle Body, for illustrations.

Note: The IMRC return springs are strong. Make sure the return springs operate properly and plates open and close fully.

Manually open and close IMRC plates at intake manifold (press IMRC lever down for Escort/Tracer) and feel for sticking/binding.

Is concern indicated?

Yes	No
GO to HU16 .	GO to HU17 .

HU16 PERFORM IMRC PHYSICAL TEST

Disconnect IMRC linkage or cables(s) from runner(s) or remove actuator assembly for Escort/Tracer.

Note: IMRC return springs are strong.

Rotate IMRC lever(s) fully open to fully closed without obstruction and contacting closed stop screw.
Feel for sticking or binding during rotation and spring tension of approximately.34 to.45 Nm (3 to 4 lb-in).

Is concern indicated?

Yes	No
CLEAN or REPAIR runners. REFER to Intake Air Distribution and Filtering, Section 303-12 in the Workshop Manual. GO to HU38 .	REPLACE IMRC actuator. GO to HU38 .

HU17 PERFORM IMRC FUNCTIONAL TEST

Connect scan tool to data link connector (DLC).
Key on, engine off.

Note: If the IMRC plates open immediately when the key is turned on, Go to HU23 .

Access Output Test Mode (OTM) (refer to Section 2 ).

WARNING: KEEP FINGERS CLEAR OF IMRC LEVER/CABLE MECHANISM.

Turn all outputs on.
When IMRC is commanded on, lever(s) should rotate to full-open position. At least one of the levers should contact the wide open stop, the other may be slightly off the wide open stop. For Escort/Tracer, IMRC actuator lever will rotate to full open position at approximately 90 degrees.

Did the IMRC lever(s) cycle from fully closed and remain fully open while all outputs were on?

Yes	No
GO to HU25 .	GO to HU18 .

HU18 CHECK IMRC ACTUATOR VPWR CIRCUIT FOR AN OPEN IN HARNESS

Disconnect IMRC actuator harness connector.
Measure VPWR circuit voltage at the IMRC actuator harness connector.

Is IMRC VPWR voltage greater than 10.5 volts?

Yes	No
GO to HU19 . For Escort/Tracer, GO to HU20 .	KEY OFF. REPAIR open circuit. GO to HU38 .

HU19 CHECK IMRC GROUND CIRCUIT FOR OPEN IN HARNESS

Measure voltage between ground and VPWR circuits at the IMRC actuator harness connector.

Is voltage greater than 10.5 volts?

Yes	No
GO to HU20 .	REPAIR open circuit. GO to HU38 .

HU20 VERIFY DRIVER CIRCUIT FUNCTION

Access Output Test Mode (OTM) (refer to Section 2 ).
Place a test lamp between VPWR and the IMRC signal circuit at the IMRC actuator harness connector.
Turn all outputs on.

Did the test lamp glow with all outputs on?

Yes	No
KEY OFF. GO to HU32 .	KEY OFF. GO to HU21

HU21 CHECK IMRC DRIVER CIRCUIT FOR OPEN IN HARNESS

Disconnect PCM.
Measure resistance of IMRC signal circuit between PCM harness connector and the IMRC actuator harness connector.

Is resistance less than 5 ohms?

Yes	No
GO to HU22 .	REPAIR open circuit. GO to HU38 .

HU22 CHECK IMRC DRIVER CIRCUIT FOR SHORT TO VPWR IN HARNESS

Key on, engine off.
Measure voltage between IMRC signal circuit at the IMRC actuator harness connector and ground.

Is voltage less than 10.5 ohms?

Yes	No
Possible intermittent concern. GO to Z1 . REPLACE PCM (refer to Section 2 , Flash EEPROM) after determining concern is not intermittent. GO to HU38 .	REPAIR short circuit. GO to HU38 .

HU23 CHECK IMRC DRIVER CIRCUIT FOR SHORT TO GROUND OR SHORT TO MONITOR CIRCUIT WITH PCM CONNECTED

Measure resistance between the IMRC driver circuit to PWR GND and then to SIG RTN and then to the monitor circuit at the IMRC harness connector.

Are all resistances greater than 10,000 ohms?

Yes	No
REPLACE IMRC. GO to HU38 .	GO to HU24 .

HU24 CHECK IMRC DRIVER CIRCUIT FOR SHORT TO GROUND OR SHORT TO MONITOR CIRCUIT WITH PCM DISCONNECTED

Disconnect PCM harness connector.
Measure the resistance between the IMRC driver circuit to PWR GND and then to SIG RTN and then to the monitor circuit at the IMRC harness connector.

Are all resistances greater than 10,000 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). GO to HU38 .	REPAIR the appropriate circuit for short. GO to HU38 .

HU25 VIEW IMRC MONITOR PID TO DETERMINE PATH FOR POSSIBLE SHORT

Note: All vehicles will display VREF for IMRCM PID except 3.8L and 4.2L which will display approximately 2.5 volts.

With the scan tool, monitor the IMRCM PID.

Is the IMRCM PID displaying either VREF or approximately 2.5 volts?

Yes	No
GO to HU26 .	GO to HU30 .

HU26 CHECK IMRC MONITOR PID TO DETERMINE A SHORT TO VPWR

With the scan tool, monitor the IMRCM PID while in Output Test Mode.
Turn all output on.

Is the IMRCM PID displaying less than 1 volt with all outputs on?

Yes	No
GO to HU27 .	GO to HU32 .

HU27 CHECK IMRC MONITOR CIRCUIT FOR SHORT TO VPWR AT IMRC HARNESS CONNECTOR

Disconnect IMRC actuator harness connector.
Key on, engine off.
Measure voltage between monitor circuit at the IMRC actuator harness connector and ground.

Is voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to HU28 .	KEY OFF. GO to HU29 .

HU28 DETERMINE SHORT TO POWER WITH PCM DISCONNECTED

Key on, engine off.
Disconnect PCM.
Measure voltage between monitor circuit at the IMRC actuator harness connector and ground.

Is voltage less than 10.5 volts?

Yes	No
KEY OFF. REPAIR short circuit. GO to HU38 .	KEY OFF. REPLACE PCM (refer to Section 2 , Flash EEPROM). GO to HU38 .

HU29 CHECK MONITOR FOR SHORT TO VPWR AT IMRC ACTUATOR

Measure actuator resistance between the monitor circuit and VPWR.

Is resistance greater than 10,000 ohms?

Yes	No
Possible intermittent concern. GO to Z1 . REPLACE PCM (refer to Section 2 , Flash EEPROM) after determining fault is not intermittent. GO to HU38 .	REPLACE IMRC actuator.HU38 .

HU30 DETERMINE IMRC MONITOR CIRCUIT SHORT TO GROUND

With the scan tool, monitor the IMRCM PID.
While viewing PID, disconnect the IMRC actuator harness connector.

Did voltage change from less than 1 volt to VREF when disconnecting the IMRC actuator harness connector?

Yes	No
KEY OFF. REPLACE IMRC actuator. GO to HU38 .	KEY OFF. GO to HU31 .

HU31 CHECK IMRC MONITOR HARNESS FOR SHORT TO GROUND

Disconnect PCM.
Measure resistance between IMRC monitor and ground (if applicable) and SIG RTN pins at the IMRC actuator harness connector.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). GO to HU38 .	REPAIR short circuit. GO to HU38 .

HU32 CHECK MONITOR CIRCUIT RESPONSE

Disconnect IMRC actuator harness connector.
With the scan tool, monitor the IMRCM PID.
Connect a jumper lead from the IMRC monitor pin to ground at the harness connector.

Did the IMRCM PID voltage cycle from VREF to less than 1 volt when inserting the jumper?

Yes	No
KEY OFF. GO to HU33 .	KEY OFF. GO to HU36 .

HU33 CHECK SIG RTN OR CHASSIS GROUND CIRCUIT CONTINUITY WITH PCM CONNECTED

Measure resistance of SIG RTN or chassis ground circuit between IMRC actuator harness connector and B-.

Is resistance less than 5 ohms?

Yes	No
GO to HU34 .	GO to HU35 .

HU34 CHECK MONITOR LINE FOR INTERMITTENT OPEN

Measure resistance of monitor line while wiggling and bending harness from IMRC harness connector to PCM harness connector.

Is the resistance fluctuating while checking the harness?

Yes	No
REPAIR intermittent open circuit. GO to HU38 .	REPLACE IMRC actuator. GO to HU38 .

HU35 CHECK SIG RTN OR CHASSIS GROUND CIRCUIT CONTINUITY WITH PCM DISCONNECTED

Disconnect PCM from harness connector.
Measure resistance of SIG RTN or chassis ground circuit between PCM harness connector and IMRC actuator harness connector.

Is resistance less than 5 ohms?

Yes	No
Possible intermittent concern. GO to Z1 . REPLACE PCM (refer to Section 2 , Flash EEPROM) after determining concern is not intermittent. GO to HU38 .	REPAIR open circuit. GO to HU38 .

HU36 CHECK MONITOR LINE CONTINUITY

Disconnect PCM from harness connector.
Measure resistance of IMRC monitor circuit between PCM harness connector and IMRC actuator harness connector.

Is resistance less than 5 ohms?

Yes	No
GO to HU37 .	REPAIR open circuit. GO to HU38 .

HU37 CHECK MONITOR CIRCUIT FOR INTERMITTENT OPEN

Measure resistance of monitor line while wiggling and bending harness from IMRC harness connector to PCM harness connector.

Is the resistance fluctuating while checking the harness?

Yes	No
REPAIR intermittent open. GO to HU38 .	REPLACE PCM (refer to Section 2 , Flash EEPROM). GO to HU38 .

HU38 IMRC REPAIR VERIFICATION DRIVE CYCLE

Key on, engine off.
Connect scan tool to data link connector (DLC)
Complete PCM reset.
Access IMRC and IMRCM PIDs.
Drive vehicle, obeying all traffic and safety laws.
Safely perform three accelerations from stop to more than 3500 rpm.
Watch for PIDs to change.
Perform Quick Test (refer to Section 4 , Diagnostic Subroutines).

Are any DTCs received?

Yes	No
GO to Section 4 , Powertrain DTC chart.	PASSED IMRC Drive cycle. No IMRC concern is present at this time.

HU65 DTC P1549: PERFORM VISUAL INSPECTION

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Inspect IMT Valve System. Check to be sure the harness is intact and the connector is firmly in place.

Is fault indicated?

Yes	No
REPAIR as necessary. REFER to the Intake Air Distribution and Filtering, Section 303-12 in the Workshop Manual for component removal procedure. VERIFY a symptom no longer exists.	Passed visual inspection. GO to HU66 .

HU66 CHECK PCM DRIVER COMMAND

Connect scan tool to data link connector (DLC).
Key on, engine running.
Access IMTV PID.
Increase engine speed to about 3500 rpm while observing IMTV PID.

Does PID read 100% then drop to 50% while rpm was above 3500?

Yes	No
KEY OFF. Passed test. GO to HU67 .	REPLACE damaged PCM. VERIFY a symptom no longer exists.

HU67 CHECK IMT VALVE ACTUATOR VPWR CIRCUIT FOR OPEN IN HARNESS

Disconnect harness connector from the actuator.
Key on, engine off.
Measure VPWR circuit voltage at the harness connector.

Was the voltage greater than 10.5 volts?

Yes	No
KEY OFF. Passed check. GO to HU69 .	REPAIR IMT valve actuator VPWR circuit for open. VERIFY a symptom no longer exists.

HU69 CHECK FOR OPEN SIGNAL CIRCUIT BETWEEN PCM AND IMT VALVE ACTUATOR

Install breakout box, leave PCM disconnected.
Measure resistance of Circuit between PCM test pin 46 and actuator harness connector.

Is the resistance less than 5.0 ohms?

Yes	No
Passed test. GO to HU70 .	REPAIR IMT Valve Actuator Signal Circuit open. VERIFY a symptom no longer exists.

HU70 CHECK IMT VALVE ACTUATOR FOR SHORT TO PWR GND

Measure resistance between PCM test pin 46 and test pin 77 or 103.

Is resistance greater than 10,000 ohms?

Yes	No
Passed check. GO to HU71 .	REPAIR IMT Valve actuator signal circuit for short to PWR GND. VERIFY a symptom no longer exists.

HU71 CHECK IMT VALVE ACTUATOR SIGNAL CIRCUIT FOR SHORT TO VPWR

Key on, engine off.
Measure voltage between PCM test pin 46 and 77 or 103.

Is the voltage less than 1 volt?

Yes	No
KEY OFF. Passed check. GO to HU72 .	REPAIR IMT Valve actuator signal circuit for short to VPWR. VERIFY a symptom no longer exists.

HU72 CHECK PCM DRIVER FOR IMT VALVE ACTUATOR

Reconnect PCM.
Connect DVOM to VPWR and signal at the harness connector.
Connect scan tool to data link connector (DLC).
Key on, engine off.
Access Output Test Mode (OTM) (Refer to scan tool instruction manual).
Take a reading with the digital Multimeter.
Command all outputs on.
Take another reading with the digital Multimeter.

Was the voltage less than 1 volt before commanding all outputs on and greater than 10.5 volts with all outputs on?

Yes	No
KEY OFF. Passed test. GO to HU73 .	REPLACE PCM (refer to Section 2 , Flash EEPROM). VERIFY a symptom no longer exists.

HU73 CHECK IMT VALVE SHUTTER FOR DAMAGE

Remove IMT Valve (Refer to the Powertrain/Engine Group of the Workshop Manual).
Visually inspect IMT valve shutter for damage.
Rotate shutter by hand.

Does the shutter bind or appear damaged?

Yes	No
Damaged shutter. REPLACE IMT valve. VERIFY a symptom no longer exists.	Passed test. Leave IMT Valve disassembled. GO to HU74 .

HU74 CHECK IMT VALVE ACTUATOR FOR COIL DAMAGE

Reconnect IMT valve harness connector.
Key on, engine off.
Access Output Test Mode (OTM) (Refer to scan tool instruction manual).
Command all outputs on.

Did the IMT valve shutter rotate when commanding all outputs on?

Yes	No
Passed check. Fault is intermittent. GO to Pinpoint Test Step Z1 .	REPLACE IMT valve actuator. VERIFY a symptom no longer exists.