Diagnostic Aids

Perform this test only when instructed by QUICK TEST, or when directed by TEST QA.

To prevent replacing good components, be aware that the following non-EEC related areas may be the cause of problem:

Fuse, bulb or socket

This test is intended to diagnose only the following:

STO/MIL circuit
ECA
Data Communications Link (DCL)

Fig 1: "CHECK ENGINE" Light Circuit

Fig 2: Data Communication Link (DCL) Circuit

3.0L PFI TEST PIN WIRE COLOR IDENTIFICATION

Application	Wire Color
Pin 9 (DATA -)	Orange
Pin 17 (STO/MIL)	White/Blue
Pin 28 (DATA +)	Orange/Yellow
Pin 40 (PWR GND)	Black/White
Pin 60 (PWR GND)	Black/Yellow

3.0L SPFI (AXODE) TEST PIN WIRE COLOR IDENTIFICATION

Application	Wire Color
Pin 17 (STO/MIL)	Tan/Red
Pin 18 (DATA +)	Orange/Black
Pin 19 (DATA -)	Black/Orange
Pin 40 (PWR GND)	Black/Light Green
Pin 60 (PWR GND)	Black/Light Green

3.0L SPFI-MA (SHO) TEST PIN WIRE COLOR IDENTIFICATION

Application	Wire Color
Pin 17 (STO/MIL)	Tan/Red
Pin 40 (PWR GND)	Black/Light Green
Pin 60 (PWR GND)	Black/Light Green

1) Malfunction Indicator Light (MIL) Always On If vehicle will not start, go to TEST A, step 1). Service all other KOEO and Continuous Memory Codes before proceeding with this test. Turn ignition off. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Connect DVOM between test pins No. 17 and 40 at breakout box. If resistance is greater than 5 ohms, replace ECA; remove breakout box and rerun QUICK TEST. If reading is less than 5 ohms, repair short between test pin No. 17 and self-test connector or CHECK ENGINE light. Remove breakout box, reconnect all components and repeat QUICK TEST.

NOTE: There is a break in the step numbering sequence at this point, skipping from step 1) to step 4). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

4) Malfunction Indicator Light (MIL) Never On: Check Continuity Of STO/MIL Circuit If vehicle will not start, go to TEST A, step 1). Turn ignition on; leave engine off. Set DVOM on 20-volt scale. Measure voltage between battery negative terminal to ground side of MIL fuse. If voltage is greater than 10.5 volts, go to step 6). If voltage is less than 10.5 volts, go to next step.

5) Check For Voltage At Fuse Set DVOM on 20-volt scale. With Key On Engine Off (KOEO), measure voltage from battery negative post to hot side of MIL fuse. If voltage is greater than 10.5 volts, repair fuse or open circuit. Reconnect ECA and verify repair by turning ignition to RUN position. If voltage is not greater than 10.5 volts, repair MIL/VBAT circuit. Reconnect ECA and verify repair by turning ignition to RUN position.

6) Check Continuity Of VBAT Circuit Turn ignition off. Set DVOM to 200-k/ohm scale. Measure resistance between MIL fuse (at ground side) and MIL bulb socket (VBAT side). If resistance is greater than 10 k/ohms, repair open circuit in MIL circuit. Verify repair by turning ignition to RUN position. If resistance is less than 10 k/ohms, go to next step.

7) Check MIL Bulb Response To Grounding Turn ignition off. Attach one end of jumper wire to negative battery terminal or chassis ground. Attach other end of jumper wire to ground side of MIL bulb socket. Turn ignition to RUN position. If MIL light comes on, turn ignition off. Remove jumper wire and go to next step. If MIL light does not come on, turn ignition off and remove jumper wire. Replace MIL bulb socket. Turn ignition to RUN position to verify operation.

8) Check Continuity Of MIL Circuit Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and leave ECA disconnected. Set DVOM to 200-ohm scale. Measure resistance between test pin No. 17 at breakout box and MIL. If resistance is less than 5 ohms, replace ECA. Remove breakout box. Verify operation by turning ignition switch to RUN position. If resistance is greater than 5 ohms, repair open MIL circuit. Turn ignition switch to RUN position to verify operation.

NOTE: There is a break in the step numbering sequence at this point, skipping from step 8) to step 10). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

10) CHECK ENGINE Or SERVICE ENGINE SOON Light Intermittent, Check For Intermittent Short From STO To Ground If vehicle does not start, go to TEST A, step 1). The light comes on when a Continuous Memory Code is present. Service all Continuous Memory Codes before proceeding. If no codes are outputted, proceed with this test. Enter KOEO wiggle test. See CONTINUOUS MONITOR MODE (WIGGLE TEST) under QUICK TEST near the beginning of this article. Observe DVOM for indication of fault while performing wiggle test on harness in the following areas:

From self-test connector to dash panel
Dash panel to ECA
Dash panel to Malfunction Indicator Light (MIL).

If a fault is indicated, repair as necessary and rerun QUICK TEST. If a fault is not indicated, then fault cannot be duplicated at this time. Testing for this fault is complete.

NOTE: There is a break in the step numbering sequence at this point, skipping from step 10) to step 15). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

15) CHECK ENGINE Or SERVICE ENGINE SOON Light Flashes With Erratic Idle: Check STI Circuit For Short To Ground Vehicle symptoms indicate STI is grounded and ECA is performing self-test without tester installed. With ignition off, disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Repair as necessary. Set DVOM on 200-k/ohm scale. Measure resistance between STI connector and engine block ground. If resistance is less than 10 k/ohms, repair short circuit. Reconnect ECA and retest. If resistance is not less than 10 k/ohms, reconnect ECA. Verify symptom and test for other rough idle symptoms.

NOTE: There is a break in the step numbering sequence at this point, skipping from step 15) to step 20). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

20) CHECK ENGINE Message Displayed If vehicle will not start, go to TEST A, step 1). Perform KOEO SELF-TEST. If result is Code 11-10-11 (pass code), repair fault in electronic message center Data Communications Link (DCL). If pass code is not displayed, service codes as required in self-test procedures.

NOTE: There is a break in the step numbering sequence at this point, skipping from step 20) to step 25). Break is due to previous chart references to these testing procedures. No test procedures have been omitted.

25) Continuous Memory Code 529: CHECK ENGINE Or CHECK DCL Message Displayed Codes 529 and 533 indicate circuit failure has occurred on Data Communications Link (DCL). These codes can occur alone or in conjunction with another code. "CHECK ENGINE" or CHECK DCL message will be displayed under the following conditions:

Code 529 indicates ECA or Data Communicator Link (DCL) circuit failure.
Code 533 indicates Data Communication Link to Electronic Instrument Cluster circuit failure.

If vehicle does not start, go to TEST A, step 1). If vehicle starts, clear Continuous Memory codes. Wait 5 minutes then rerun KOEO SELF-TEST. If result is Code 11-10-11 (pass code), repair fault in electronic message center Data Communications Link (DCL). If pass code is not displayed, service codes as described in self-test procedures.