TF95 - Check TSS Wiring

Continuous Memory Diagnostic Trouble Code (DTC) 639 indicates that sometime during the last 80 warm-up cycles an error was detected in the Transmission Speed Sensor (TSS) input signal.

Possible causes:
- Intermittent open or shorted harness.
- Intermittent fault in TSS.
- Transmission fluid drained and refilled (if, within one minute of the first start after a transmission fluid change, the vehicle is put in gear, a Continuous Memory DTC 639 could be set due to an insufficient time for the new transmission fluid to fill all the cavities).

- Key "OFF".

- Visually check the TSS wires for obvious concerns. Service as necessary.

- Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

- Install breakout box. Connect PCM to breakout box.

- DVOM to 20 volts scale.

- Connect Digital Volt/Ohm Meter (DVOM) between test pin 24 and test pin 44 at breakout box.

- Start engine.

- Observe DVOM for a fault indication while performing the following (the voltage should remain stable. A fault will be indicated by the voltage becoming erratic or dropping to zero):

CAUTION: While performing this Diagnostic Test Mode test mode, use caution not to touch any moving engine parts.

- Shake, wiggle, bend the TSS(+) and TSS(-) circuits from the transmission to the PCM.

- Lightly shake and tap the transmission connector, EEC-IV connector and other related harness connectors.

- Is a fault indicated?

Yes -- Isolate fault and service as necessary. Clear continuous memory. Clearing Diagnostic Trouble Codes

Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)

No -- Key "OFF". Go to TF96. TF96 - Check PCM and Harness Connectors