DTC P0121: ACCEL POS SENSOR VOLTS DO NOT AGREE W/IDLE VALID SIGNAL

Monitor & Set Conditions

Accelerator Pedal Position Sensor (APPS) voltage is monitored with the throttle at less than 15 percent of full throttle for about one second or when the vehicle speed is greater than 10 MPH for about one second. DTC may be stored if the idle valid signal indicates an idle condition while APPS signal voltage does not indicate an idle condition or if the idle valid signal does not indicate an idle condition while APPS signal voltage indicates an idle condition.

Possible Causes

• 5-volt Supply Circuit Shorted To Voltage With Ignition On
• APP Sensor
• Idle Valid Signal (IVS) #2 Circuit Shorted To Voltage
• Sensor Ground Circuit Open
• 5-volt Supply Circuit Shorted To Voltage With The Engine Running
• ECM

Testing

1. Turn ignition off. Disconnect APPS harness connector. APPS is located on a bracket, just above fuel injection pump. Start engine and allow the engine to idle. Using DVOM, measure voltage at terminal No. 5 (Dark Blue/White wire) on APPS harness connector. If the voltage is greater than 5.5 volts, go to next step. If the voltage is 5.5 volts or less, go to step 3.

2. Turn ignition off. Turn ignition on with engine off. Using DVOM, measure voltage at terminal No. 5 (Dark Blue/White wire) on APPS harness connector. If the voltage is greater than 5 volts, repair short to voltage on Dark Blue/White wire between APPS and ECM when the ignition is on. ECM is located on driver's side of the engine, just in front of fuel transfer pump and contains a 50-pin connector. If the voltage is 5 volts or less, repair short to voltage on Dark Blue/White wire between APPS and ECM when the engine is running.

3. Turn ignition off. Using DVOM, measure resistance between ground and terminal No. 4 (Black/Yellow wire) on APPS connector. If resistance is 10 ohms or greater, go to next step. If resistance is less than 10 ohms, replace APPS. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

4. Start engine and allow the engine to idle. Turn ignition off. Turn ignition on with engine off. Using DVOM, measure voltage at terminal No. 2 (Light Green/Dark Blue wire) on APPS harness connector. If the voltage is 5.5 volts or less, go to next step. If the voltage is greater than 5.5 volts, repair short to voltage on Light Green/Dark Blue wire between APPS and ECM. ECM is located on driver's side of the engine, just in front of fuel transfer pump and contains a 50-pin connector.

5. Turn ignition off. Disconnect ECM harness connector. ECM is located on driver's side of the engine, just in front of fuel transfer pump and contains a 50-pin connector. Using DVOM, measure the resistance of Black/Yellow wire between terminal No. 4 on APPS harness connector and terminal No. 32 on ECM connector. If resistance is 10 ohms or greater, repair open in Black/Yellow wire between APPS and ECM. If resistance is less than 10 ohms, replace and program the ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

If you find that your APPS is bad you can replace it with a Timbo Apps from the Mopar1973man Store.