Here's one for the AW4 experts.
Noticed recently that my 90XJ (189K) no longer engages the TC lockup either in Drive or No 3 GearShift position. Also I noticed no change in shift points while engaging the power/comfort switch. The transmission shifts smoothly and at the correct RPMs as far as I can tell (except for the TC lockup). This has reduced my gas mileage to about 15MPG so I'm trying to correct. Things I've checked at the TCU computer are:
Verified pulses at C3 input while vehicle is moving (approx 6VDC on/off).
Verified power/comfort switch voltage input at TCU connector with switch on.
Verified continuity at TCU connector for solenoids 1 thru 3 (approx 12 ohms).
Verified voltage at TCU connector for brake pedal input (only present with brake depressed).
Verified continuity at TCU connector back to TPS inputs.
Verified TPS resistance range/changes while manually moving throttle to full open (engine off)
Verified TCU inputs fron Neutral Safety Switch (NSS recently removed and cleaned)
Verified TCU connector fused battery voltage inputs (including ignition switch)
Connecting a voltmeter to the solenoid 3 output at the TCU connector reveals 0VDC with car at 50mph and in Drive position. I didn't check solenoids 1 and 2 since the transmission shifts fine otherwise. Jumpering battery voltage to the terminal will engage the TC lockup.
Transmission fluid is red in color and at full mark with vehicle hot.
Vehicle has ABS brakes but didn't see any overlap with TCU.
Could the TCU be bad?? The question is why won't the TCU do it and why doesn't the power/comfort switch appear to have any effect?
Will a TCU from a 1994XJ work (MPI to Renix)? I have a spare but didn't want to plug and play without research.
Noticed recently that my 90XJ (189K) no longer engages the TC lockup either in Drive or No 3 GearShift position. Also I noticed no change in shift points while engaging the power/comfort switch. The transmission shifts smoothly and at the correct RPMs as far as I can tell (except for the TC lockup). This has reduced my gas mileage to about 15MPG so I'm trying to correct. Things I've checked at the TCU computer are:
Verified pulses at C3 input while vehicle is moving (approx 6VDC on/off).
Verified power/comfort switch voltage input at TCU connector with switch on.
Verified continuity at TCU connector for solenoids 1 thru 3 (approx 12 ohms).
Verified voltage at TCU connector for brake pedal input (only present with brake depressed).
Verified continuity at TCU connector back to TPS inputs.
Verified TPS resistance range/changes while manually moving throttle to full open (engine off)
Verified TCU inputs fron Neutral Safety Switch (NSS recently removed and cleaned)
Verified TCU connector fused battery voltage inputs (including ignition switch)
Connecting a voltmeter to the solenoid 3 output at the TCU connector reveals 0VDC with car at 50mph and in Drive position. I didn't check solenoids 1 and 2 since the transmission shifts fine otherwise. Jumpering battery voltage to the terminal will engage the TC lockup.
Transmission fluid is red in color and at full mark with vehicle hot.
Vehicle has ABS brakes but didn't see any overlap with TCU.
Could the TCU be bad?? The question is why won't the TCU do it and why doesn't the power/comfort switch appear to have any effect?
Will a TCU from a 1994XJ work (MPI to Renix)? I have a spare but didn't want to plug and play without research.