Diagnostic Aids
Perform this test only when directed by QUICK TEST. To prevent replacing good components, be aware following non-EEC areas may be at fault:
- Engine base condition (cam timing, valves rings, etc.).
- Electrical (alternator, battery, add-on devices, etc.).
- Transmission shift linkage.
This test is not intended to diagnose transmission. This test is intended to diagnose:
- Wiring harness circuits MLP, TSR, TSL, TSD, TSOD and SIG RTN.
- ECA.
| Application | Wire Color |
|---|---|
| Continental, Crown Victoria, Grand Marquis, Sable, Taurus & Town Car | Light Blue/Yellow |
| Application | Wire Color |
|---|---|
| Continental, Crown Victoria, Grand Marquis, Sable, Taurus & Town Car | Gray/Red |
1) KOEO Codes 67/634, 522 & 654 KOEO Codes 67/634 522 and 654 indicate MLP sensor is out of self-test range (3770-4607 ohms) when gear selector is in PARK position. Possible causes for these faults are:
- Linkage not adjusted correctly.
- Faulty Manual Lever Position (MLP) sensor.
- Circuit open or grounded.
- Faulty ECA.
Turn ignition off. Apply parking brake. Place transmission gear selector in NEUTRAL position. Place Manual Lever Position (MLP) sensor gauge in sensor slot. If gauge does not fit, loosen MLP mounting bolts and adjust sensor as necessary. If gauge fits, go to step 2).
2) Check MLP Sensor Circuit Continuity Turn ignition off. Disconnect MLP sensor wiring harness connector. 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 MLP terminal at MLP sensor wiring harness connector and test pin No. 30 at breakout box. Measure resistance between SIG RTN terminal at MLP sensor wiring harness connector and test pin No. 46 at breakout box. If either resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST . If both resistances are 5 ohms or less, go to step 3).
3) Check MLP Sensor For Short To Power & Ground Turn ignition off. Leave ECA and MLP sensor disconnected. Measure resistance between test pin No. 30 and test pins No. 40, 46 and 60 at breakout box. Measure resistance between test pin No. 30 and chassis ground. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If resistance is 10,000 ohms or more, go to step 4).
4) Check MLP Sensor Resistance Turn ignition off. Connect MLP sensor. Leave ECA disconnected from breakout box. Measure resistance between test pins No. 30 and 46 at breakout box while cycling gear selector. See MLP SENSOR RESISTANCE . If resistance is within specification, replace ECA and repeat QUICK TEST . If resistance is not within specification, replace MLP sensor and repeat QUICK TEST.
| Gear Selected | Ohms |
|---|---|
| Park | 3770-4607 |
| Reverse | 1304-1593 |
| Neutral | 660-807 |
| Overdrive | 361-442 |
| Drive | 190-232 |
| First | 78-95 |
7) Incorrect Shift/No Shift Turn ignition off. Check transmission fluid. Add or replace as necessary. Test drive vehicle to determine transmission shift patterns. If transmission always remains in 3rd gear when vehicle is operated with shift lever in DRIVE or OVERDRIVE position, go to step 8). If transmission does not operate as described, go to step 11).
8) Visual Inspection Visually check select switch and solenoid wiring harness between ECA and transmission. Repair or replace wiring harness as necessary. If wiring harness is okay, go to step 9).
9) Diagnose Transmission Shift Patterns If transmission upshifts and downshifts correctly, EEC-IV system is okay. Fault is in transmission. If transmission does not shift correctly, check harness and connectors for intermittent opens and shorts.
10) Code 634 Code 634 indicates ECA has received incorrect voltage signals from gear select sensors. Clear continuous memory codes. Start engine. Shift gear selector to each position, leaving selector in each gear for 10 seconds. Turn ignition off. Shift gear selector to PARK position. Perform KOEO SELF-TEST . If Code 634 is not present, fault is intermittent. Go to step 20). If Code 634 is present, go to step 11).
11) Check IGN START/RUN Circuit At Transmission Turn ignition off. Disconnect 4EAT wiring harness connector at transmission. Turn ignition on. Measure voltage between IGN START/RUN terminal at transmission wiring harness connector. If voltage is less than 10.5 volts, repair open circuit and repeat QUICK TEST . If voltage is 10.5 volts or more, go to step 12).
12) Check Transmission Select Switches Turn ignition off. Disconnect transmission switch and neutral drive switch. Check transmission select switch specifications. See Fig 3 and Fig 4 . If connector terminal values are not correct, go to step 14). If connector terminal values are correct, go to step 13).
13) Check Transmission Switch Input Voltage Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV) or 4EAT tester, leaving ECA disconnected. Reconnect transmission switch. Turn ignition on. Check test pins listed in 4EAT TRANSMISSION SELECT SWITCH VOLTAGE AT EEC-IV BREAKOUT BOX. See Fig 3 and Fig 4 . If voltage values are correct, replace ECA and repeat QUICK TEST. If voltage values are not correct, repair circuit.
14) MLP Switch Turn ignition off. Check circuits and connectors for damage and corrosion. Ensure MLP switch is adjusted correctly. See step 1). If any faults are found, repair or replace as necessary. If no faults are found, replace MLP switch.
20) Recheck For Code 634 Clear continuous memory codes. Turn ignition on. Shake and bend select switch wiring harness circuit between ECA and transmission. Shift gear selector through entire range and then place in PARK position. Perform KOEO SELF-TEST . If Code 634 is present, isolate fault and repair as necessary. If Code 634 is not present, go to step 21).
21) Inspect Circuit Turn ignition off. Inspect transmission switches and harness connectors for corrosion and damaged pins. Inspect wiring harness for incorrect routing. If any faults are found, repair or replace as necessary. If no faults are found, problem is intermittent and cannot be found at this time.