P2135, P2138 Accelerator Pedal Position (APP) assembly failure, Powertrain Control Module (PCM) failure, Throttle Position Sensor (TPS) failure

Land Rover OBD-II Trouble Codes -------------------------------------------------The diagnostic trouble codes (DTCs) P2135 and P2138 both relate to issues with the Accelerator Pedal Position (APP) assembly and the Throttle Position Sensor (TPS). Additionally, P2138 mentions a potential Powertrain Control Module (PCM) failure. Here's a breakdown of each code:

1. **P2135 - Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation:**

   - This code indicates that there is a correlation issue between the voltages of Throttle Position Sensor A and Throttle Position Sensor B within the Accelerator Pedal Position (APP) assembly.

2. **P2138 - Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation:**

   - Similar to P2135, but this code specifically refers to Throttle Position Sensor D and Throttle Position Sensor E within the APP assembly.

### Possible Causes:

1. **Faulty Accelerator Pedal Position (APP) Assembly:** Issues with the assembly that houses the accelerator pedal position sensors.

2. **Accelerator Pedal Position Sensor Issues:** Malfunctioning or out-of-range Throttle Position Sensors within the APP assembly.

3. **Wiring Issues:** Problems with the wiring or connectors associated with the APP assembly circuit.

4. **Powertrain Control Module (PCM) Issues:** A potential failure or malfunction in the PCM, which controls and monitors various aspects of the engine and throttle system.

### Diagnostic Steps:

1. **Inspect Accelerator Pedal Position (APP) Assembly:** Check the APP assembly for signs of damage or wear. If it appears faulty, consider replacement.

2. **Check Wiring and Connectors:** Inspect the wiring and connectors associated with the APP assembly circuit. Look for any signs of damage, corrosion, or loose connections.

3. **Test Accelerator Pedal Position Sensors:** Use a multimeter or diagnostic tool to test the Throttle Position Sensors within the APP assembly. Check for proper resistance or voltage readings.

4. **Perform Continuity Tests:** Check for continuity in the wiring from the APP assembly to the PCM.

5. **Verify PCM Operation:** Test the PCM for proper operation. Replace if necessary.

6. **Clear Codes:** After addressing any identified issues, clear the trouble codes and monitor the system for recurrence.

7. **Consider Professional Assistance:** If you are unsure about diagnosing or addressing these issues yourself, or if the faults persist, it's advisable to consult with a qualified mechanic or technician.

Addressing the root cause of the APP assembly and TPS faults is crucial for proper accelerator pedal response and overall engine performance. If in doubt or if the faults persist, seeking professional assistance is recommended for a thorough diagnosis and effective repair.