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DTC P122C or P122D - LNP or LNQ

The throttle body is a normally open valve and is only operated during diesel particulate filter (DPF) regeneration and when maintaining the selective catalyst reduction temperature. The position of the valve is controlled by the engine control module (ECM). The throttle body system uses a motor to move the valve to an open or closed position and a position sensor located within the valve assembly is used to monitor the position of the valve.

The throttle body uses a motor to move the valve to an open or closed position.

P122C 00

P122D 00

P122C 00

The ECM detects a short circuit on the throttle valve control circuit voltage for greater than 3 s.

P122D 00

The ECM detects that the difference between the desired throttle valve position and the actual throttle valve position is greater than 10% or less than -10%.

or

The ECM detects that the learnt throttle valve offset position at open or closed position is greater than 20% or less than -20%.

or

The ECM detects that the difference between the maximum and minimum throttle valve position learnt at open or closed position is greater than 30%.

DTCs P122C or P122D are Type B DTCs.

DTCs P122C or P122D are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Observe the scan tool DTC information parameter. DTC P02E0 00, P02E1 00, P02E2 00, P02E3 00, P02E8 00, P02E9 00, P02EB 00, or P122B 00 should not set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Ignition ON, command the Inlet Air Flow Valve Position from 0-95% with a scan tool. The throttle blade should respond to the scan tool commands.
3. Engine ticking over, observe the scan tool Inlet Air Flow Valve Position Sensor parameter. The reading should be between 3.7-4.7 V.
4. Turn OFF the ignition while observing the scan tool Inlet Air Flow Valve Position Sensor parameter. The parameter should fluctuate between 0-100% several times
5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

1. Ignition OFF, inspect the Q38 Throttle Body for the following conditions:

•	A throttle blade that is not in the rest position

•	A throttle blade that is binding open or closed

•	A throttle blade that opens or closes without spring pressure

•	Throttle body for dirt, debris or coking

•	A damaged throttle valve blade or shaft

⇒	If a condition is found, clean or replace the Q38 Throttle Body.

2. Ignition OFF, disconnect the harness connector at the Q38 Throttle Body.
3. Test for less than 5 Ω between the ground circuit terminal 4 and ground.

⇒	If greater than the specified range, repair the ground circuit for an open/high resistance.

4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 5 and ground.

⇒	If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

5. Verify the scan tool Inlet Air Flow Valve Position Sensor parameter is less than 0.3 V.

⇒	If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

6. Install a 3 A fused bridging wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 5. Verify the scan tool Inlet Air Flow Valve Position Sensor parameter is at 4.8-5.2 V.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

7. If all circuits test normal, replace the Q38 Throttle Body.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.