Diagnostic Aids

Perform this test when checking computed timing or if directed by QUICK TEST  . This test is intended to diagnose:

• SAW wiring harness circuit.
• Base timing.
• Faulty ECA.

To prevent replacing good components, be aware following non-EEC related areas may be at fault:

• Basic engine condition (valves, vacuum leaks, valve timing, etc.).
• EDIS module.

Fig 1: EDIS Connector Terminal ID (1.9L)

Fig 2: EDIS Connector Terminal ID (4.6L)

1) Check For Power To ECA  Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Turn ignition on. Measure voltage between test pins No. 37 and 40 at breakout box. Measure voltage between test pins No. 57 and 60 at breakout box. If both readings are 10.5 volts or more, go to step 2). If either reading is less than 10.5 volts, go to CIRCUIT TEST B.

2) Check SAW Circuit For Continuity  Turn ignition off. Disconnect EDIS module. Measure resistance between test pin No. 36 at breakout box and SAW terminal at EDIS module wiring harness connector. See Fig 3 . If resistance is 5 ohms or less, go to step 3). If resistance is more than 5 ohms, repair open circuit. Reconnect all components, and check ignition timing.

Fig 3: Module Connector Terminal ID

3) Check SAW Circuit For Shorts To Power (Except VREF)  Turn ignition off. Leave ECA and EDIS module disconnected. Measure voltage between test pin No. 36 and test pin No. 40 or 60 at breakout box. To check for short to VBAT, turn ignition off. To check for short to VPWR, turn ignition on. If any reading is more than 10.5 volts, repair short circuit and repeat QUICK TEST  . If voltage is 10.5 volts or less, go to step 4.

4) Check SAW Circuit For Shorts To VREF, Ground & PIP  Turn ignition off. Leaving ECA and EDIS module disconnected. To check for shorts to ground, measure resistance between test pin No. 36 and test pins No. 16, 20, 40, 46 and 60. To check for shorts to VREF, measure resistance between test pins No. 26 and 36. To check for shorts to PIP circuit, measure resistance between test pins No. 36 and 56. If each resistance is more than 10,000 ohms, go to step 5). If resistance is 10,000 ohms or less, repair short circuit. Reconnect all components, and repeat QUICK TEST  .

During this test, a short to SIG RTN (pin No. 46) may be indicated along with an actual short to PWR GND when 4-wire HEGO is connected to vehicle wiring harness.

5) Check SAW Voltage at ECA  Turn ignition off. Connect ECA to breakout box. Reconnect EDIS module. Place timing switch on breakout box in DIST position. Set DVOM on 20-volt AC scale. Start engine. Measure voltage between test pin No. 36 and negative battery terminal. If AC voltage is not within specification, replace ECA and repeat QUICK TEST  . See TEST PIN NO. 36 (SAW) VOLTAGE SPECIFICATIONS  . If AC voltage within specification, EEC-IV system is okay. Remove breakout box, reconnect ECA and check ignition system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.