| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. If DTCs P0100, P0101, P0110, P0115 and P0120 are output together, inspect ECM E2 circuit (sensor ground) between terminal No. 18 (Brown wire) at ECM harness connector E4 and splice E2. Repair as necessary. See WIRING DIAGRAMS article.
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
TP sensor is a variable resistor which monitors throttle opening. ECM determines vehicle driving condition and adjusts air/fuel mixture accordingly. DTC is set when ECM consistently detects less than .1 volt or more than 4.9 volts on VTA circuit. Possible causes are
- TP sensor circuit is open or shorted.
- Defective TP sensor.
- Defective ECM.
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 open or shorted. If percentage displayed on scan tool is always 100 percent, E2 circuit may be open. Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.