Diagnosis & Repair
- Access ECM behind bottom center of instrument panel, in front of console. Turn ignition on. Using DVOM, backprobe and measure voltage between terminals No. 1 (Yellow wire) and No. 9 (Brown wire) at ECM harness connector E5. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
- Using DVOM, backprobe ECM harness connector and measure voltage between terminals No. 7 (Blue/Yellow wire) and No. 9 (Brown wire) at ECM harness connector E5. Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and less than .5 volt with 1.18 in. Hg applied. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
- Check for open or short in wiring between vapor pressure sensor and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.