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Diagnosis & Repair

  1. Access ECM harness connectors behind glove box. Turn ignition on. Backprobing ECM harness connector, measure voltage between terminals No. 1 (Blue/Red wire) and No. 22 (Brown wire) at ECM E13 connector. 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 and retest.
  2. Backprobing ECM harness connector, measure voltage between terminals No. 18 (Pink/Green wire) at ECM E11 connector and No. 22 (Brown wire) at ECM E13 connector. Disconnect vacuum hose from vapor pressure sensor. Voltage reading should be as follows:
    • 3.0-3.6 volts with no vacuum applied.
    • 4.2-4.8 volts with .22 psi (1.5 kPa) applied.
    • 1.3-2.1 volts with .59 in. Hg (2.0 kPa) applied.

    If voltage is as specified, replace ECM and retest. If voltage is not as specified, go to next step.

  3. Check for an open or short in wiring harness between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace vapor pressure sensor.
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