P0122-THROTTLE POSITION SENSOR 1 CIRCUIT LOW





For a complete wiring diagram Refer to Section 8W.



Possible Causes
(F855) 5-VOLT SUPPLY CIRCUIT OPEN
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K22) TP SIGNAL 1 CIRCUIT SHORTED TO GROUND
(K22) TP SIGNAL 1 CIRCUIT SHORTED TO THE (K922) TP RETURN CIRCUIT
THROTTLE POSITION SENSOR/THROTTLE BODY
PCM


Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. ACTIVE DTC

NOTE: If a 5-Volt Supply DTC has also set, diagnose the 5-Volt DTC before continuing.

NOTE: When this DTC is Active the engine speed, torque, and vehicle speed are limited to a Limp in mode.


Ignition on, engine not running.
With a scan tool, select View DTCs.

Is the DTC Active at this time?

Yes


No

2. P0222 ALSO SET


Was the P0222-TP SENSOR NO.2 VOLTAGE LOW DTC set along with the P0122?

Yes


No

3. (F855) 5-VOLT SUPPLY CIRCUIT



Turn the ignition off.
Disconnect the Throttle Body harness connector.
Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit in the Throttle Body harness connector.

Is the voltage between 4.8 to 5.2 volts?

Yes


No

4. THROTTLE POSITION SENSOR

With a scan tool, monitor the TP Sensor No.1 voltage with the Sensor harness connector disconnected.

Is the voltage above 4.5 volts?

Yes


No

5. (K22) TP SIGNAL 1 CIRCUIT SHORTED TO GROUND



Turn the ignition off.
Disconnect the C2 PCM harness connector.
Measure the resistance between ground and the (K22) TP Signal 1 circuit in the Throttle Body harness connector.

Is the resistance below 100 ohms?

Yes


No

6. (K22) TP SIGNAL 1 CIRCUIT SHORTED TO THE (K922) TP RETURN CIRCUIT



Measure the resistance between the (K22) TP Signal 1 circuit and the (K922) TP Return circuit in the Throttle Body harness connector.

Is the resistance below 100 ohms?

Yes


No

7. (F855) 5-VOLT SUPPLY CIRCUIT OPEN



Turn the ignition off.
Disconnect the C2 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnostics.


Measure the resistance of the (F855) 5-volt Supply circuit from the Throttle Body harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes


No

8. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND



Measure the resistance between ground and the (F855) 5-volt Supply circuit in the Throttle Body harness connector.

Is the resistance below 100 ohms?

Yes


No

9. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.


Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes


No

10. THROTTLE FOLLOWER TEST

With a scan tool, perform the Throttle Follower Test.
Monitor the TP Sensor No.1 voltage.

Does voltage start at approximately 0.8 of a volt and go above 3.5 volts with a smooth transition?

Yes


No