Diagnostic Aids
Enter this test when directed by QUICK TEST. This test is only intended to diagnose:
- Harness circuits (SIG RTN and OCT ADJ).
- Octane shorting bar connector.
Purpose of Octane Adjust Shorting Bar is to provide optimum spark advance for fuel used. If engine detonates (spark knock), remove Octane Shorting Bar. This retards spark advance about 3-4 degrees. If engine continues to detonate, use fuel with a higher octane rating.
| Application | Wire Color |
|---|---|
| Crown Victoria & Grand Marquis | White/Red |
| Escort & Tracer | Green/White |
| Mustang 2.3L & Town Car | Dark Green |
| Taurus 3.0L SHO | Pink |
| Thunderbird 3.8L SC | Gray/White |
| Application | Wire Color |
|---|---|
| Escort & Tracer | Light Green/Black |
| Except Escort & Tracer | Gray/Red |
1) Code 57/341 Code 57/431 indicates Octane Adjust Shorting Bar is not in place or OCT ADJ circuit is open. Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar has been removed, go to step 2). If shorting bar is in place, go to step 4).
2) Check For Modification Decal If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If vehicle does not have modification decal, go to step 3).
3) Check For Code 57/341 Replace OCT ADJ shorting bar. Perform KOEO SELF-TEST . If Code 57/341 is present, go to step 4); If code is not present, testing is complete. If driveability faults are present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
4) Check Octane Adjust Circuit Continuity Continuity should exist from OCT ADJ circuit, through in-line connector and shorting bar, to SIG RTN circuit. 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. Measure resistance between test pin No. 46 and OCT ADJ test pin at breakout box. If resistance is more than 5 ohms, repair open OCT ADJ circuit, shorting bar or SIG RTN circuit. Repeat QUICK TEST . If resistance is 5 ohms or less, replace ECA and repeat QUICK TEST.
5) Check For Code 11 Start engine. Warm it to normal operating temperature. Turn ignition off. Perform KOEO SELF-TEST . If Code 11 or 111 is present, go to step 6). If Code 11 or 111 is not present, use higher octane fuel or check for other possible causes for Code 57/341. For all other codes, return to QUICK TEST .
6) Verify In-Line Shorting Bar Is Installed Turn ignition off. Inspect Octane Adjust in-line connector. If shorting bar is installed, go to step 8). If shorting bar is not installed, go to step 7).
7) Check For Modification Decal If vehicle has modification decal indicating OCT ADJ shorting bar was removed as a factory authorized procedure, testing is complete. If engine is detonating, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If vehicle does not have modification decal, go to step 10).
8) Check For Technical Service Bulletin (TSB) If a TSB authorizing removal of OCT ADJ shorting bar exists, go to step 9). If a TSB authorizing removal of OCT ADJ shorting bar does not exist, testing is complete. If driveability faults are present, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
9) Verify Drive Concern Turn ignition off. Locate and remove shorting bar. Test drive vehicle to verify complaint. If detonation is present, go to step 10). If detonation is not present, EEC-IV is okay; testing is complete.
10) Check Octane Adjust Circuit For Short To Ground 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. Measure resistance between OCT ADJ circuit at in-line connector and test pins No. 40 and 60 at breakout box. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST . If each resistance is more than 10,000 ohms, go to step 11).
11) Check ECA Turn ignition off. Disconnect OCT ADJ shorting bar. Turn ignition on. Measure voltage between breakout box OCT ADJ test pin terminal and test pins No. 40 and 60. If voltage is less than 4 volts, replace ECA. If engine still detonates, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section. If voltage is 4 volts or more, remove breakout box and go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section.