Diagnosis & Repair

Access ECM harness connectors behind glove box. Connect Check Harness "A" (SST 09990-01000) to ECM. See TEST PREPARATION under SELF-DIAGNOSTIC SYSTEM. Turn ignition on. Remove air intake duct. Disconnect sub-throttle actuator connector. See Fig 1. Measure voltage between ground and terminal No. 42 (Yellow/Blue wire) at ECM "B" connector. See Figure.
Voltage should be .3-.8 volt (throttle closed) and 3.2-4.9 volts (throttle open). Measure voltage between ground and terminal No. 63 (Red/Black wire) at ECM "B" connector. Voltage should be 0-3 volts (throttle closed) and 9-14 volts (throttle open). If voltage is not as specified, go to next step. If voltage is as specified, no problem is detected at this time. Problem is intermittent.
Disconnect SUB-TP sensor connector. See Fig 1. Measure resistance between terminals No. 1 (Brown wire) and No. 3 (Yellow/Blue wire) at SUB-TP sensor. Resistance should be 200-800 ohms (throttle closed) and 2400-11,200 ohms (throttle open).
Measure resistance between terminals No. 1 (Brown wire) and No. 2 (Red/Black wire) at SUB-TP sensor. Resistance should be less than 500 ohms (throttle closed) and infinite (throttle open). If resistances are as specified, go to next step. If resistances are not as specified, adjust SUB-TP sensor. See ON-VEHICLE ADJUSTMENTS article. If adjustment is okay, replace sensor.
Check for open or short in wiring harness between SUB-TP sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.

Fig 1: Identifying Throttle Body Connectors (Models With TRAC)