Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose:

Wiring harness circuits TSS and OSS.
ECA.

Fig 1: Transmission Speed Sensor Ckt. (Escort & Tracer - 4EAT)

Fig 2: Transmission Speed Sensor Ckt. (Continental, Sable & Taurus - AXOD-E; Crown Victoria, Grand Marquis & Town Car - AOD-E)

TEST PIN NO. 5 (OSS OR TSS) WIRE COLOR ID

Application	Wire Color
Sable & Taurus	Green/Black
Continental, Crown Victoria, Grand Marquis & Town Car	Dark Green/White

1) KOER Code 639 KOER Code 639 indicates input from Turbine Speed Sensor (TSS) or Output Shaft Speed (OSS) to ECA is out of calibration. Possible causes for these faults are:

Faulty TSS or OSS sensor.
Circuit open or grounded.
Faulty ECA.

Turn ignition off. Disconnect suspect sensor. 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 OSS or TSS terminal at sensor wiring harness connector and test pin No. 5 at breakout box. Measure resistance between SIG RTN terminal at sensor wiring harness connector and test pin No. 46 at breakout box. If either resistance is more than 5 ohms, repair short circuit and repeat QUICK TEST . If both resistances are 5 ohms or less, go to step 2).

2) Check Circuit For Short To Power Or Ground Turn ignition off. Leave sensor disconnected. Measure resistance between test pin No. 5 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 5 and test pins No. 40, 46 and 60 at breakout box. If either resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST . If both resistances are 10,000 ohms or more, go to step 3).

3) Measure Sensor Resistance Turn ignition off. Leave sensor disconnected. Measure resistance between sensor terminals. OSS terminal resistance should be 450-750 ohms. TSS circuit resistance should be 80-200 ohms. If resistance is not correct, replace sensor and repeat QUICK TEST . If resistance is correct, replace ECA and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted.

10) Code 639 Code 639 indicates incorrect input signal from TSS. Possible causes for this fault are:

Faulty TSS.
Circuit open or grounded.
Faulty ECA.

Turn ignition off. Disconnect transmission 12-pin connector. Measure resistance between TSS (-) and TSS (+) terminal at sensor wiring harness connector. If resistance is not 200-600 ohms, check wiring for damage and corrosion. If wiring is okay, replace TSS. If resistance is 200-600 ohms, go to step 11).

11) Check TSS Circuit For Short To Power Turn ignition off. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Turn ignition on. Measure voltage between TSS (+) terminal at sensor wiring harness connector and chassis ground. Measure voltage between TSS (-) terminal at sensor wiring harness connector and chassis ground. If both voltages are less than 0.5 volt, go to step 12). If either voltage is 0.5 volt or more, repair short circuit and repeat QUICK TEST .

12) Check TSS Circuit For Short To Ground Turn ignition off. Leave transmission connector and ECA disconnected. Measure resistance between TSS (+) terminal at sensor wiring harness connector and chassis ground. Measure resistance between TSS (-) terminal at sensor wiring harness connector and chassis ground. Measure resistance between TSS (+) and TSS (-) terminals at sensor wiring harness connector. If any resistance is less than 10,000 ohms, repair short circuit and repeat QUICK-TEST. If any resistance is 10,000 ohms or more, go to step 13).

13) Check TSS Circuit Continuity Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV) or 4EAT tester, leaving ECA disconnected. Leave transmission wiring harness connector removed. Measure resistance between TSS (+) terminal at sensor wiring harness connector and test pin No. 24 at breakout box. Measure resistance between TSS (-) terminal at sensor wiring harness connector and test pin No. 44 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 14).

14) Check ECA For Internal Shorts

Turn ignition off. Connect ECA to breakout box. Leave transmission wiring harness connector removed. Measure resistance between test pin No. 24 and pins No. 37, 40, 44, 57 and 60 at breakout box. If any resistance is less than 500 ohms, replace ECA and repeat QUICK TEST . If each resistance is 500 ohms or more, go to step 15).

15) Check TSS Output Turn ignition off. Leave ECA connected to breakout box. Attach transmission wiring harness connector. Set DVOM on AC voltage scale. Start engine. Measure voltage between breakout box test pins No. 24 and 44 while varying engine speed. If AC voltage varies more than 0.5 volt, replace ECA and repeat QUICK TEST . If AC voltage does not vary more than 0.5 volt, replace TSS and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 639 Code 639 indicates ECA detected incorrect output signal from OSS or TSS during previous 40-80 warm-up cycles. Possible causes for this fault are:

Faulty OSS or TSS.
Circuit open or grounded.
Faulty ECA.

Record and clear continuous memory codes. While test driving vehicle, stop, ensure transmission gear selector is in DRIVE position and accelerate heavily to 35 MPH. After test drive, perform QUICK TEST and record all codes. If Continuous Memory Code 639 does not repeat, problem cannot be duplicated at this time. If Continuous Memory Code 639 is repeated, go to step 91).

91) Check OSS Or TSS Circuit Continuity 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. Disconnect OSS or TSS wiring harness connector. Measure resistance at TSS or OSS terminal at sensor wiring harness connector and test pin No. 5 at breakout box. Measure resistance at SIG RTN terminal at sensor wiring harness connector and test pin No. 5 at breakout box. If either resistance is less than 500 ohms, repair short circuit and repeat QUICK TEST . If both resistances are 500 ohms or more, go to step 92).

92) Check Circuit For Short To Power Or Ground Turn ignition off. Leave sensor disconnected. Measure resistance between test pin No. 5 and test pins No. 37 and 57 at breakout box. Measure resistance between test pin No. 5 and test pins No. 40, 46 and 60 at breakout box. If either resistance is less than 500 ohms, repair short circuit and repeat QUICK TEST . If both resistances are 500 ohms or more, go to step 93).

93) Measure Sensor Resistance Turn ignition off. Leave sensor disconnected. Measure resistance between sensor terminals. OSS terminal resistance should be 450-750 ohms. TSS circuit resistance should be 80-200 ohms. If resistance is correct, replace ECA and repeat step 90) to verify code elimination. If resistance is not correct, replace sensor and repeat step 90) to verify code elimination.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 93) to step 95). No test procedures have been omitted.

95) Continuous Memory Code 639 Continuous Memory Code 639 indicates an error in TSS sensor output during previous 80 warm-up cycles. Possible causes for this fault are:

Intermittent fault in TSS sensor.
Intermittent short or open in wiring harness.

Turn ignition off. Visually inspect TSS wires and connectors for damage. Disconnect 60-pin ECA connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Connect ECA to breakout box. Connect DVOM between test pins No. 24 and 44 at breakout box. Start engine. Shake and bend TSS wires between transmission and ECA. Lightly tap circuit connectors. Voltage should remain stable or change gradually. If voltage drops or surges abruptly, fault in circuit is indicated. If fault is indicated, isolate and repair as necessary. If no faults are found, problem cannot be located at this time.