2014 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P0122-THROTTLE POSITION SENSOR 1 CIRCUIT LOW

Special Tools: Click to display a list of tools used in this procedure


For a complete wiring diagram, refer to the Wiring Information.


Theory of operation

The Electronic Throttle Control (ETC) system uses two Throttle Position Sensors (TPS) to monitor the throttle blade position. The Throttle Position Sensors 1 and 2 are located within the Throttle Body assembly. Each sensor has a 5-Volt reference circuit, a low reference circuit, and a signal circuit. Processors are also used to monitor the ETC system data. The processors are located within the Powertrain Control Module (PCM). Each signal circuit provides the processors with a signal voltage proportional to throttle blade movement. The processors share and monitor data to verify that the indicated TPS calculation is correct.


Possible Causes

(F855) 5-VOLT SUPPLY CIRCUIT OPEN
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO GROUND
(K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO THE (K922) TP SENSOR RETURN CIRCUIT
(K22) TP SENSOR NO.1 SIGNAL CIRCUIT OPEN
THROTTLE POSITION SENSOR/THROTTLE BODY
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)



NOTE: Diagnose and repair any Throttle Body circuit, system voltage or sensor supply voltage DTCs before continuing with this test.
1. Start the engine and allow it to reach operating temperature.

WARNING:

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. With the scan tool, read the active DTCs.

NOTE: If the DTC does not reset it may be necessary to test drive the vehicle.

NOTE: If the P2122-APP Sensor 1 Circuit Low DTC is also Active, diagnose the P2122 before continuing with the P0122 diagnostic procedure.


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
1. Turn the ignition off.
2. Disconnect the Throttle Body harness connector.
3. Ignition on, engine not running.
4. 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

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


NOTE: The sensor voltage should be approximately 5.0 Volts (plus or minus .1 volt) with the connector disconnected.


Does the scan tool display the voltage as described above?

Yes


No


5. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM C2 harness connector.
3. Measure the resistance between ground and the (K22) TP Sensor No.1 Signal circuit in the Throttle Body harness connector.


Is the resistance below 100 Ohms?

Yes


No


6. (K22) TP SENSOR NO.1 SIGNAL CIRCUIT SHORTED TO THE (K922) TP SENSOR RETURN CIRCUIT
1. Measure the resistance between the (K22) TP Sensor No.1 Signal circuit and the (K922) TP Sensor Return circuit in the Throttle Body harness connector.


Is the resistance below 100 Ohms?

Yes


No


7. EXCESSIVE RESISTANCE IN THE (K22) TP SENSOR NO.1 SIGNAL CIRCUIT

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 the GPEC Diagnostic Adaptor to perform the diagnosis.

1. Connect the Adapter, GPEC Diagnostic 10436 .
2. Measure the resistance of the (K22) TP Sensor No.1 Signal circuit between the Throttle Body harness connector and the GPEC Adaptor.


Is the resistance below 5.0 Ohms?

Yes


No


8. (F855) 5-VOLT SUPPLY CIRCUIT OPEN

1. Turn the ignition off.
2. Disconnect the PCM C2 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 the GPEC Diagnostic Adaptor to perform the diagnosis.

3. Connect the Adapter, GPEC Diagnostic 10436 .
4. Measure the resistance of the (F855) 5-Volt Supply circuit from the Throttle Body harness connector to the GPEC Adaptor.


Is the resistance below 5.0 Ohms?

Yes


No


9. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and the (F855) 5-Volt Supply circuit at the Throttle Body harness connector.


Is the resistance below 100 Ohms?

Yes


No


10. POWERTRAIN CONTROL MODULE (PCM)

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Throttle Body and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.


Were there any problems found?

Yes


No


11. THROTTLE FOLLOWER TEST

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


Does the voltage start at approximately 0.7 Volt and increase to approximately 4.3 Volts with a smooth transition?

Yes


No