On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

DP: Vehicle Speed Sensor (VSS)/Transfer Case Speed Sensor (TCSS)

DP: Introduction

DP1 DTC P0500/P0501/P1502: CHECK VSS CIRCUITS FOR OPEN IN HARNESS (VRS TYPE)

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

Disconnect PCM.
Disconnect VSS.
Measure resistance of VSS+ circuit between PCM harness connector pin and VSS+ sensor harness connector.
Measure resistance of VSS- circuit between PCM harness connector pin and VSS- sensor harness connector.

Is each resistance less than 5.0 ohms?

Yes	No
GO to DP2 .	REPAIR open circuit. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).

DP2 CHECK VSS CIRCUITS FOR SHORT TO GROUND AND POWER IN HARNESS

Measure resistance between VSS+ and PWR GND circuits at PCM harness connector.
Measure resistance between VSS+ and VSS- circuits at PCM harness connector.
Measure resistance between VSS+ and VPWR circuits at PCM harness connector.

Is each resistance greater than 5.0 ohms?

Yes	No
GO to DP3 .	GO to DP12 .

DP3 CHECK VSS RESISTANCE

Measure VSS resistance.

Is resistance between 170 and 270 ohms?

Yes	No
REPLACE the PCM (refer to Section 2 , Flash EEPROM). COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	REPLACE the VSS. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).

DP5 DTC P0500/P0501/P1502: CHECK VSS SIGNAL OUTPUT TO (PCM) POWERTRAIN CONTROL MODULE (HALL TYPE)

Disconnect PCM.
Raise the vehicle to allow rotation of the front drive wheel.
Key on, transmission in NEUTRAL.

Note: The opposite wheel must be held stationary.

Measure voltage between VSS+ and PWR GND circuits at the PCM harness connector, while slowly rotating the drive wheel.
The voltage should rise above 5.0 volts and fall below 1.0 volt in a regular cycle. Observe several cycles.
Key off.

Does the VSS output voltage rise and fall as specified while slowly rotating the drive wheel?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	GO to DP6 .

DP6 CHECK VOLTAGE BETWEEN VPWR AND PWR GND CIRCUITS AT VSS

Disconnect VSS.
Key on.
Measure voltage between VPWR and PWR GND circuits at the VSS harness connector.

Is the voltage greater than 10.5 volts?

Yes	No
GO to DP7 .	KEY OFF. GO to DP10 .

DP7 CHECK VSS CIRCUIT FOR SHORT TO POWER IN HARNESS

Key on.
Measure voltage between VSS+ and PWR GND circuits at the PCM harness connector.
Key off.

Is voltage less than 1.0 volt?

Yes	No
GO to DP8 .	GO to DP12 .

DP8 CHECK VSS CIRCUIT FOR SHORT TO GROUND IN HARNESS

Measure resistance between VSS+ and PWR GND circuits at the PCM harness connector.

Is resistance greater than 3,000 ohms?

Yes	No
GO to DP9 .	GO to DP12 .

DP9 CHECK VSS SIGNAL CIRCUIT FOR OPEN IN HARNESS

Measure resistance of VSS+ signal circuit between PCM harness connector pin and VSS+ sensor harness connector.

Is resistance less than 5.0 ohms?

Yes	No
REPLACE VSS. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	REPAIR open circuit. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).

DP10 CHECK VSS GROUND CIRCUIT FOR OPEN IN HARNESS

Measure resistance of PWR GND circuit between VSS harness connector and chassis ground.

Is resistance less than 5.0 ohms?

Yes	No
REPAIR open VPWR to VSS. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	REPAIR open VSS PWR GND circuit. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).

DP12 VERIFY IF VSS CIRCUIT IS SHORTED IN HARNESS OR ANOTHER MODULE

Determine which, if any, modules are connected to the VSS circuit (Refer to Wiring Diagrams Manual). If no other modules are connected to the VSS circuit, GO to the "YES" Action To Take.
One at a time, disconnect the modules associated with the VSS circuit. After disconnecting each module, again test for short circuit (Refer to test step that sent you here). Repeat until each associated module has been disconnected or the short circuit has been eliminated.

Does the short circuit remain after all associated modules were disconnected?

Yes	No
REPAIR short circuit. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	GO to the Workshop Manual for further diagnosis of appropriate module.

DP15 KOER DTC P1501: CHECK PCM VSS PID FOR INPUT SIGNAL

Start the engine and idle in NEUTRAL.
Access the VSS PID with a scan tool and observe for vehicle speed input to the PCM.
Increase the engine speed, not greater than 2000 rpm, several times while observing the VSS PID.

Is the reading on the VSS PID less than 5 km/h (3 mph)?

Yes	No
Unable to duplicate or identify fault at this time. If DTC P1501 still exists. GO to Pinpoint Test Step, Z1 . (REFER to Section 4 , Diagnostic Trouble Code [DTC] Descriptions for a list of possible causes.)	GO to DP22 .

DP20 DTC P0503: INSPECT VSS AND CIRCUIT FOR AN INTERMITTENT

Check for harness intermittents by verifying that Pins are properly seated in connector shell, wiring is properly crimped, no corrosion exists in the harness and sensor is securely mounted.

Are there any indications of harness intermittents?

Yes	No
REPAIR as necessary. COMPLETE an OBDII Drive Cycle (REFER to Section 2 , Drive Cycles).	GO to DP21 .

DP21 CHECK PCM VSS PID FOR INPUT SIGNAL

Access the VSS PID with a scan tool.
Drive the vehicle at several steady state speeds above and below 50 km/h (30 mph).

Note: For Scan Tools which have Data Record feature, record data for playback to help identify variations.

During each steady state speed observe the VSS PID for variations of (+) or (-) 8 km/h (5 mph) for greater than 10 seconds.

Is there any indications of a noisy or intermittent signal with the VSS PID?

Yes	No
GO to DP22 .	Unable to duplicate or identify fault at this time. REPAIR any other DTCs.

DP22 CHECK VSS HARNESS ROUTING

Check VSS harness routing:

Verify that the harness is not routed adjacent to high current wires such as ignition wires or generator wiring.
Verify VSS harness is shielded and grounded, if applicable.
Check resistance of the VSS harness; refer to Pinpoint Test Schematic and Connectors at beginning of pinpoint test.

Are any concerns evident?

Yes	No
REPAIR as necessary. COMPLETE an OBDII Drive Cycle (REFER to Section 2 , Drive Cycles).	Unable to duplicate or identify a fault at this time. GO to Pinpoint Test Step Z1 . (REFER to Section 4 , Diagnostic Trouble Code [DTC] Descriptions for a list of possible causes.)

DP25 DTC P1500: VISUAL INSPECTION

Visually inspect the VSS and VSS harness circuits for any potential failures. Use the following check list for reference:

Loose VSS connector.
Pushed out VSS connector pins.
Damaged VSS wiring harness insulation.
Incorrect harness routing.
Incorrect VSS mounting.

Did the visual inspection reveal a potential failure?

Yes	No
REPAIR fault as necessary. COMPLETE an OBD II Drive Cycle (REFER to Section 2 , Drive Cycles).	RESTORE vehicle. Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 . (REFER to Section 4 , Diagnostic Trouble Code [DTC) Descriptions for a list of possible causes.)

DP30 DTC P0500, P1502 VISUAL INSPECTION

Note: The transfer case speed sensor (TCSS) provides rotational speed of output shaft of the transfer case. The PCM use this information to control powertrain behavior and on some applications is used as the source of vehicle speed information.

Disconnect TCSS sensor.
Inspect TCSS vehicle harness connector for damage and proper seating.

Have any problems been found?

Yes	No
REPAIR as necessary.	GO to DP31 .

DP31 CHECK RESISTANCE OF TCSS SENSOR

Measure resistance between TCSS signal and TCSS SIGTRN circuits at the TCSS sensor.

Is resistance between 1,000 and 1,250 ohms?

Yes	No
GO to DP32 .	REPLACE TCSS sensor.

DP32 TCSS OUTPUT CHECK

Measure frequency between TCSS signal and TCSS SIGRTN circuits at the TCSS sensor.
Drive vehicle between 0 and 48 km/h (0 and 30 mph).
Refer to Section 6 , Reference Values for freuqency ranges.

Does frequency reading increase and decrease with vehicle speed?

Yes	No
GO to DP33 .	REMOVE the TCSS and inspect target wheel. REPAIR as necessary. IF OK REPLACE TCSS.

DP33 CHECK HARNESS FOR SHORT TO PWR

Key on.
TCSS sensor disconnected.
Measure voltage between the TCSS signal circuit at the TCSS harness connector and ground.

If voltage less than 1.0 volt?

Yes	No
KEY OFF. GO to DP34 .	REPAIR short circuit.

DP34 CHECK HARNESS FOR OPEN

Disconnect PCM.
Measure resistance of TCSS signal circuit between PCM harness connector pin and TCSS sensor harness connector.
Measure resistance of TCSS SIGRTN circuit between PCM harness connector pin and TCSS sensor harness connector.

Is each resistance less than 5.0 ohms?

Yes	No
GO to DP35 .	REPAIR open circuit.

DP35 CHECK HARNESS FOR SHORT TO GROUND

Measure resistance between TCSS signal and SIGRTN circuits at the TCSS harness connector.
Measure resistance between TCSS signal and GND circuits at the TCSS harness connector.

Is each resistance greater than 10,000 ohms?

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