Diagnostic Aids
PCM uses switch inputs to judge the level of electrical load on engine. As electrical load on engine increases, PCM may increase idle speed to compensate. Perform this test only when directed here. This CIRCUIT TEST is intended to diagnose:
- Daytime Running Light (DRL) switch and circuit.
- Headlamp (HDLP) switch and circuit.
- Defroster (DEF) switch and circuit.
CIRCUIT PIN IDENTIFICATION
| Circuit | Breakout Box Pin No. | PCM Pin | Wire Color |
|---|---|---|---|
| DEF SW | 19 | C1-25 | Purple |
| DRL SW | 7 | C1-15 | Green |
| HDLP | 11 | C1-11 | White |
- 1) Check Switch PID Turn ignition off. Connect NGS scan tool to OBD-II DLC. Turn ignition on. Access desired PID. Observe PID as switch is operated on and off. If PID does not indicate ON and OFF as expected, go to next step. If PID indicates ON and OFF as expected, go to CIRCUIT TEST Z or the TESTS W/O CODES - 2.5L article for intermittent diagnostics.
- 2) Check Input Voltage Switching Turn ignition off. Install breakout box. Leave PCM disconnected. Inspect PCM connector for pushed out pins, corrosion, loose wires, etc. Measure voltage at breakout box test pin in question as switch is turned ON and OFF. If voltage cycles between 0-12 volts, replace PCM. If voltage does not cycle between 0-12 volts, go to next step.
- 3) Check For Open Circuits Disconnect switch in question. Install breakout box. Leave PCM disconnected. Measure resistance between test pin of switch in question and signal pin at switch connector. Resistance should be less than 5 ohms. Measure resistance between test pin in question and ground. Resistance should be greater than 10,000 ohms. If resistance measurements are not as specified, repair open or shorted circuit. Repeat QUICK TEST . If resistance measurements are correct, replace switch in question. Repeat QUICK TEST .