On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

DH: Throttle Position (TP) Sensor

DH1 KOEO AND KOER DTC P1124: CHECK FOR OTHER DTCS

Check for DTC P1400 in KOEO or KOER Self-Test.

Is KOEO or KOER DTC P1400 present with KOEO DTC P1124?

Yes	No
RETURN to Section 4 , Powertrain Diagnostic Trouble Code Charts for DTC P1400.	KEY OFF. GO to DH2 .

DH2 CHECK FOR STUCK THROTTLE PLATE OR LINKAGE

Visually inspect the throttle linkage and throttle plate for binding or sticking.
Verify the throttle plate and linkage is at closed throttle position.

Does the throttle move freely and return to closed throttle position?

Yes	No
Throttle plate and linkage are OK. GO to DH8 .	REPAIR as necessary.

DH3 DTC P1120: CHECK TP CIRCUIT FOR FRAYED WIRES OR CORROSION ON CONNECTORS

Key off.
Complete a visual inspection of pins on harness connector at the TP sensor for corrosion.
Complete a visual inspection of the harness wires between the TP sensor and the PCM for insulation fraying and corrosion.

Is a fault present?

Yes	No
REPAIR as necessary.	GO to DH4 .

DH4 CHECK FOR STUCK TP SENSOR

Key on, engine off.
Access TP PID (TP V PID).
Slowly move throttle from closed throttle position to wide open throttle position and observe the TP PID (TP V PID).

While opening the throttle, is the TP PID (TPV PID) reading below 9.85% (0.49 volt)?

Yes	No
KEY OFF. GO to DH5 .	GO to DH20 .

DH5 CHECK VOLTAGE BETWEEN VREF AND SIG RTN CIRCUITS TO TP SENSOR

Disconnect TP sensor.
Key on, engine off.
Measure voltage between VREF and SIG RTN circuits at the TP sensor harness connector.

Is voltage between 4.0 and 6.0 volts?

Yes	No
KEY OFF. GO to DH6 .	GO to Pinpoint Test Step C1 .

DH6 CHECK TP CIRCUIT FOR OPEN IN HARNESS

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

Disconnect PCM.
Measure resistance of TP circuit between PCM harness connector pin and TP harness connector.

Is resistance less than 5.0 ohms?

Yes	No
GO to DH7 .	REPAIR open circuit.

DH7 CHECK TP SENSOR VOLTAGE TO PCM

Reconnect PCM and TP sensor.
Start engine and idle for 2 minutes.
Access TP PID (TP V PID).
Slowly open the throttle from closed position and observe PID(s).

Is TP PID (TP V PID) reading at any time between 3.42-9.85% (0.17-0.49 volt)?

Yes	No
REPLACE TP sensor.	If DTC P1120 is still present, GO to DH20 .

DH8 DTC P0123 OR P1124: ATTEMPT TO GENERATE THE OPPOSITE THROTTLE POSITION ANGLE (VOLTAGE) PID READING

Disconnect TP sensor.
Key on, engine off.
Access TP PID (TP V PID).

Is TP PID (TP V PID) less than 3.42% (0.17 volt)?

Yes	No
GO to DH9 .	KEY OFF. GO to DH10 .

DH9 CHECK VOLTAGE BETWEEN VREF AND SIG RTN CIRCUITS TO TP SENSOR

Key on, engine off.
Measure voltage between VREF and SIG RTN circuits at the TP sensor harness connector.

Is voltage between 4.0 and 6.0 volts?

Yes	No
REPLACE TP sensor.	GO to Pinpoint Test Step C1 .

DH10 CHECK TP CIRCUIT FOR SHORT TO VREF OR VPWR IN HARNESS

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

Disconnect PCM.
Measure resistance between TP and VPWR circuits at the PCM harness connector.
Measure resistance between TP and VREF circuits at the PCM harness connector. (For LS6/LS8 measure to both VREF pins.)

Is each resistance greater than 10,000 ohms?

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

DH11 DTC P0122: ATTEMPT TO GENERATE THE OPPOSITE THROTTLE POSITION ANGLE (VOLTAGE) PID READING

Note: An intermittent fault can cause a Continuous Memory DTC P0122. If a Continuous Memory DTC P0122 is still present after DH11 through DH14, go to DH20 .

Disconnect TP sensor.
Jumper VREF circuit to TP circuit at the TP sensor harness connector.
Key on, engine off.

Note: If any scan tool communication concern exists, remove jumper and go to DH14 .

Access TP PID (TP V PID).

Is TP PID (TP V PID) greater than 93% (4.65 volts)?

Yes	No
REPLACE TP sensor.	REMOVE jumper. GO to DH12 .

DH12 CHECK VOLTAGE BETWEEN VREF AND SIG RTN CIRCUITS

Key on, engine off.
Measure voltage between VREF and SIG RTN circuits at the TP sensor harness connector.

Is voltage between 4.0 and 6.0 volts?

Yes	No
KEY OFF. GO to DH13 .	GO to Pinpoint Test Step C1 .

DH13 CHECK TP SENSOR CIRCUIT FOR OPEN IN HARNESS

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

Disconnect PCM.
Measure resistance of TP circuit between PCM harness connector pin and TP sensor harness connector.

Is resistance less than 5.0 ohms?

Yes	No
GO to DH14 .	REPAIR open circuit.

DH14 CHECK TP CIRCUIT FOR SHORT TO PWR GND OR SIG RTN IN HARNESS

Disconnect PCM.
Disconnect scan tool from DLC.
Measure resistance between TP and PWR GND circuits at the PCM harness connector.
Measure resistance between TP and SIG RTN circuits at the PCM harness connector.

Are both resistances greater than 10,000 ohms?

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

DH15 DTC P1121: CHECK RATIONALITY OPERATION BETWEEN TP AND MAF SENSORS

Attempt to start engine.

Does the engine run?

Yes	No
GO to DH16 .	CHECK for major leaks, cracks, and openings between MAF sensor and throttle body. If OK, GO to Pinpoint Test Step A1 .

DH16 CHECK MECHANICAL OPERATION OF TP SENSOR

Key on, engine off.
Access TP PID (TP V PID).
Slowly move throttle from closed throttle position to wide open throttle position.
Observe and record the TP PID (TP V PID).

While opening and closing the throttle, is there a change in the TP PID (TP V PID) between 9.85% and 93% (0.49 and 4.65 volts)?

Yes	No
GO to DH17 .	REPLACE TP sensor. VERIFY a symptom no longer exists.

DH17 CHECK TP SENSOR SIGNAL HIGH VERSUS THE ENGINE LOAD WHILE DRIVING VEHICLE

Key on, engine running.
Drive vehicle, exercising the throttle and TP sensor while accessing PIDS.
Access TP PID (TP V PID) and LOAD PID and record readings.

Is TP PID (TP V PID) greater than 49.02% (2.44 volts) and the LOAD PID reading less than 30%?

Yes	No
LISTEN for air noise around MAF sensor and throttle body while engine is running. REPAIR if necessary. Otherwise, GO to HU1 for air restriction. If OK, REPLACE the TP sensor.	GO to DH18 .

DH18 CHECK TP SENSOR SIGNAL LOW VERSUS THE ENGINE LOAD WHILE DRIVING VEHICLE

Note: If the vehicle is a no start, go to Pinpoint Test Step A1 .

Drive vehicle exercising the throttle and TP sensor near higher gears (preferably overdrive) while accessing PIDS.
Access TP PID (TP V PID) and LOAD PID.

Is TP PID (TP V PID) reading less than 4.82% (0.24 volts) and the LOAD PID reading greater than 55%?

Yes	No
TIGHTEN TP sensor to throttle body if necessary. CLEAR Continuous Memory DTCs. DRIVE vehicle exercising the throttle. If Continuous Memory P1121 is now present, REPLACE MAF sensor.	Unable to identify the fault at this time. If vehicle is still a No Start, GO to Pinpoint Test Step A1 .

DH20 CONTINUOUS MEMORY DTCS P1120 OR P1125: CHECK FOR TP CIRCUIT INTERMITTENT SIGNAL

Start engine and bring to idle.
Run throttle up to 1500 rpm for 5 seconds.
Access TP PID (TP V PID) for a fault indication while completing the following:

Lightly tap on TP sensor and wiggle harness connector to simulate road shock.

Is TP PID (TP V PID) changing below the minimum 9.85% (0.49 volt) or above the maximum 93% (4.65 volts)?

Yes	No
INSPECT the TP sensor connector. If OK, REPLACE the TP sensor.	KEY OFF. GO to DH21 .

DH21 CHECK TP SENSOR HARNESS FOR INTERMITTENT OPENS OR SHORTS

Again access the TP PID (TP V PID).
Key on, engine off.
Complete the following:

Grasp the vehicle harness closest to the TP sensor connector.
Shake and bend a small section of the harness all the way to the dash panel.
Wiggle, shake and bend the harness from the dash panel to the PCM.

Is TP PID (TP V PID) reading changing below the minimum 9.85% (0.49 volt) or above the maximum 93% (4.65 volts)?

Yes	No
ISOLATE and REPAIR as necessary.	Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

DH22 DTC P0121: CHECK FOR KOER SELF-TEST COMPLETION

Start engine, bring to idle (throttle closed).
Activate Key On Engine Running (KOER) Self-Test.

Is DTC P0121 present or does KOER Self-Test fail to terminate?

Yes	No
GO to DH23 .	VERIFY a symptom no longer exists.

DH23 ATTEMPT TO RECREATE DTC P0121 OR DRIVEABILITY SYMPTOM

Note: If KOER Self-Test terminates when placing the transmission range selector lever in gear (DRIVE or REVERSE), GO to DH24 directly.

Attempt to drive vehicle, while still in Key On Engine Running Self-Test.
Key off, wait 15 seconds.
Start engine again.
Activate KOER Self-Test.

Is DTC P0121 still present or does KOER Self-Test again fail to terminate?

Yes	No
KEY OFF. GO to DH24 .	VERIFY a symptom no longer exists.

DH24 CHECK TP AND SIG RTN CIRCUITS FOR OPEN IN HARNESS

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

Disconnect PCM and TP sensor.
Measure resistance of TP circuit between PCM harness connector and TP sensor harness connector.
Measure resistance of SIG RTN circuit between PCM harness connector and TP sensor harness connector.

Is each resistance less than 5.0 ohms?

Yes	No
REPLACE TP sensor. VERIFY a symptom no longer exists.	REPAIR open circuit. VERIFY a symptom no longer exists.