98 auto trans problem in overdrive
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Diesel Fan
Joined: Sep 2010
Posts: 18
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From: Live Oak CA
98 auto trans problem in overdrive
Going down the road at 45mph my tranny kicks into overdrive and I mean kick sometimes it clunks in and out if I hover around 48 mph every other gear is smooth it only goes in hard in overdrive
This is the famous converter locking and unlocking.
24 Valve APPS
Rewire Ground Instructions
1994+
Lock-Up-O/D shuttle/hunt
Symptoms: At steady throttle usually at approx 40-50 MPH the tachometer will rise and fall approx 150-200 RPMS as the Torque Converter Clutch engages and dis-engages.
Problem: Electrical noise in the conducting wires running from the PCM (power train control module) to the TPS ( throttle position sensor).
This may be verified by observing a scanner while the complaint is occurring. The PCM will command loc-up on &off, the transmission is only doing what it is being told. This is not a "transmission " problem. Working on the transmission will not fix the problem. The PCM reacts to monitored voltage spikes caused by the TPS power and signal wires picking up electrical noise from other wires in the harness. The primary culprit is the AC voltage produced by the alternator. Replacing TPS’s,sensors, or PCM reflash almost never fixes the problem.
Solution: Make sure both batteries are in good condition. Make sure all battery cable connections are clean and tight. Make sure all ground connections are not corroded, this applies to PCM, TPS, and all ground connections on chassis and engine. After rewire it is sometimes required to "re-learn " the TPS (APPS on 98.5 +). Here’s how: disconnect both batteries for 15 minutes, reconnect batteries, turn ignition switch to run position (do not crank engine), slowly depress the accelerator pedal to the floor and release, turn key off. Now you may start engine and road test to verify complaint is fixed. There is a very rare occurrence of the PCM itself being defective, this is the exception not the rule. Try the most economical fix first!
http://www.suncoastconverters.com/im...d%20rewire.pdf
24 Valve APPS
Rewire Ground Instructions
1994+
Lock-Up-O/D shuttle/hunt
Symptoms: At steady throttle usually at approx 40-50 MPH the tachometer will rise and fall approx 150-200 RPMS as the Torque Converter Clutch engages and dis-engages.
Problem: Electrical noise in the conducting wires running from the PCM (power train control module) to the TPS ( throttle position sensor).
This may be verified by observing a scanner while the complaint is occurring. The PCM will command loc-up on &off, the transmission is only doing what it is being told. This is not a "transmission " problem. Working on the transmission will not fix the problem. The PCM reacts to monitored voltage spikes caused by the TPS power and signal wires picking up electrical noise from other wires in the harness. The primary culprit is the AC voltage produced by the alternator. Replacing TPS’s,sensors, or PCM reflash almost never fixes the problem.
Solution: Make sure both batteries are in good condition. Make sure all battery cable connections are clean and tight. Make sure all ground connections are not corroded, this applies to PCM, TPS, and all ground connections on chassis and engine. After rewire it is sometimes required to "re-learn " the TPS (APPS on 98.5 +). Here’s how: disconnect both batteries for 15 minutes, reconnect batteries, turn ignition switch to run position (do not crank engine), slowly depress the accelerator pedal to the floor and release, turn key off. Now you may start engine and road test to verify complaint is fixed. There is a very rare occurrence of the PCM itself being defective, this is the exception not the rule. Try the most economical fix first!
http://www.suncoastconverters.com/im...d%20rewire.pdf
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