| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
Circuit Description
The TP sensor is a variable resistor that monitors throttle opening. TP sensor is mounted in throttle body. The ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC P0120 is set when ECM consistently detects less than .1 volt on VTA circuit. DTC P0120 is also set if ECM consistently detects 4.9 volts or more on VTA circuit. Possible causes are
- Open or short in TP sensor circuit.
- Faulty TP sensor.
- Faulty ECM.
Note. If DTCs P0110, P0115 and P0120 are output together, inspect ECM terminal E2 (ground) circuit for an open. Repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article.
Diagnostic Aids
After confirming DTC P0120, use scan tool to access CURRENT DATA to confirm throttle valve opening percentage with throttle open and closed. If percentage displayed on scan tool is always zero percent, VC circuit may be open or VTA circuit may be shorted. If percentage displayed on scan tool is always 75 percent, E2 circuit may be open. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.