Originally Posted by Co_94_PU

Need this to stick in the old brain, so type it out, if it doesn't stick I can refer back here..

Much like the engine the transmission has an electronic diagnostic system. This system will flash a warning indicator, and store codes, aswell it outputs various data on a diagnostic port. The warning lamp used is the "O/D off lamp". Various faults will pulse the indicator on and off when the ignition is switched to the run position, similar to the CEL.

The first step is the same as an engine fault, verify the battery voltage is above the threshold (11 volts or greater). Next verify the indicator lamp is functional, with the key in the run position toggle the OD from on to off the indicator should light indicating the bulb is functional. Return the OD switch to the on position, which turns off the indicator or the will not flash codes and stay lit.

Enter diagnostics by turning the key to the run position, ensure the OD switch is in the on position, locate and ground the DG terminal. The DG is located on the diagnostic sub assembly on the left hand inner fender, a single wire female spade terminal.

Once the DG is grounded the indicator (OD off lamp) will flash sequences similar to the CEL where a steady flashing indicates no errors(0.25second duration). These flash patterns are located in the manual, page 606 AT-112 in an 88 pdf. Codes are cancelled by removing the "STOP fuse" for a minimum of 10 seconds (temperature dependant).

• 42, Defective speed sensor #1 (in the dash cluster). Severed wire or short circuit.
• 51, Defective speed sensor #2 (in transmission). Severed wire short circuit.
• 62, solenoid #1
• 63, solenoid #2
• 64, lockup solenoid
• 65, solenoid #4

Consult manual pages 607-609 AT113-115 for flow charts for each code.

Next perform preliminary checks.

• Fluid level, vehicle level engine running cycle into each gear from Park to Low then return to park. Verify fluid level with stick.
• Chain driven transfer, remove fill plug inspect fluid is within 10mm of plug.
• Line pressure cable, throttle plate fully open, cable stop 0-1mm to rubber boot (to-do, need length of boot protrusion)
• Shift lever (transmission), operating freely, indicator accurateness.
• Neutral start switch, starter disable unless in Park or Neutral.
• Shift lever (transfer), operates freely, indicator accurateness.
• Transfer indicator switch, accurateness.
• Engine idle speed.

Next perform Manual shift tests, to isolate trouble to electrical or mechanical.

• Disconnect ECT computer (located at the front of the lever housing, may need to remove trim)
• If indistinct perform road test.
• Park, locked.
• R, reverse gear.
• L, 1st gear.
• 2, 3rd gear.
• D, Overdrive.

If not as indicated, there is a mechanical fault.

... Consult manual for electrical control circuit flow charts page 614+ AT-120 ...

​​​​​​Inspect ECT sensor signals, page 622 AT-128

1. TPS signal, ignition to run, measure voltage at DG, throttle closed less than 1volt, voltage steps with throttle angle, throttle open greater than 8volt
2. Brake signal, with throttle fully open voltage drops from 8 volts to 0 volts when brake pedal is depressed.
3. Inspect upshift.

• ​​​​​​warm up engine, coolant temp 176°
• OD switch to on
• Pattern select to Norm
• Road test, verify voltage corisponding with gear position and lockup activations.

1. 1st gear, 0v
2. 2nd gear, 2v
3. 2nd gear lockup, 3v
4. 3rd gear, 4v
5. 3rd gear lockup, 5v
6. O/D, 6v
7. O/D lockup, 7v

Note, infrequent lockup occurs in 2nd and 3rd gears. At less than 50% throttle stroke lockup may not occur and voltage will skip over 2nd and 3rd gear lockups (2-4-6, voltage sequences)


...Consult manual, Page 623 AT-129. Perform ECT ECU and component inspections. ...

Stall test and Shift lag. (Stall test above in seperate post)
Shift lag limits.
Neutral to Drive, 1.5 seconds.
Neutral to Reverse, 1.2 seconds.

.......
​​​​​​​And we will stop here because it gets to pressure and road testing, and my memory bank is full I think.