Diagnostic Aids

Perform this test when instructed by QUICK TEST  . To prevent replacement of good components, be aware following non-EEC related areas may be at fault:

• Damaged vacuum hoses.
• Damaged Backpressure Transducer (BPT).
• EGR valve.
• EVP sensor.

This test is only intended to diagnose:

• EVR solenoid.
• ECA.
• EVR and VPWR harness circuits.

EVR solenoid regulate vacuum to EGR valve by way of Backpressure Transducer (BPT). When energized, EVR opens a port between manifold vacuum and EGR valve. When not energized, EVR closes port to EGR and vacuum is vented to atmosphere.

Fig 1: EGR Valve Regulator (EVR) Solenoid Ckts. & Connector Term.

1) Code 558  Code 558 indicates failure in EVR solenoid circuit. Possible causes for this fault are:

• Faulty EVR solenoid.
• Faulty vacuum hoses.
• Open or ground circuit in wiring harness.
• Faulty ECA.

Turn ignition off. Remove scan tester (if applicable). Disconnect cruise control servo wiring harness connector. Connect DVOM negative lead to STO terminal at Self-Test connector. Connect positive lead to positive battery terminal. Install a jumper wire between STI terminal and SIG RTN terminal at Self-Test connector. See Figure -Figure