A/T - Harsh Shifting, Transmission in Limp Mode
GROUP: 37NUMBER: 91-08
DATE: 12/20/91
SUBJECT:
Harsh Shifting/Transmission Goes Into Limp Mode
MODEL(S):
100 (With AG - 4 Automatic Transmission) M.Y. 1991
CONDITION:
Breaks in the transmission wiring harness caused by too much tension in the wiring harness between the routing/retaining clamps (arrows).
POSSIBLE CAUSE:
This condition causes open circuits in the harness which may register as one or more faults in the solenoid valves and/or defective transmission electronic control unit (ECU). (Faults could be sporadic).
SERVICE SOLUTION:
Remove multi-point connector from transmission electronic control unit (ECU).
Carefully remove rear slide cover on the back of the plug to gain access to the pin number sequence.
Disconnect external solenoid valve plug (A) at transmission.
Use tool VAC 1598 and adapter VAC 1598/09 if available.
With an ohm meter check continuity between wires at plug (A) and transmission control unit multi-point connector.
Note:
A paper clip can be used as a test probe in plug (A) when performing resistance checks.
Important:
To verify an open circuit, it may be necessary to pull or move the wiring harness between the body and transmission while checking continuity with an ohm meter.
Note:
Break usually occurs in harness near body clamp (arrow).
Cut open harness, solder broken wires and insulate using heat shrink tubing (locally available).
Remove body retaining clamp (arrow) and save fastener.
Turn clamp around in opposite direction (arrow). Install onto the same stud to relieve wiring harness tension.
Important:
Some vehicles are equipped with more than one body fastening stud. Always select the stud which will optimize the routing position of the transmission harness.
Note:
If fastener is damaged, use a speed clip on the stud to secure the clamp.
Reconnect external solenoid valve plug and transmission control unit multi-point connector.
Clear fault codes from transmission. Reset basic setting. Road test vehicle.