C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Torque converter not locking up

Old 07-25-2001, 08:13 PM
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The other day noticed my TC wasnt locking up anymore, i went to work and when i drove home it was fine, then it started to act up again so i changed my tranny fluid and filter. Didnt help. I just went for a drive with a multimeter and checked for voltage in the aldl port. I was getting a constant 12 volts it dropped to 5 when i hit the brakes so the break switch is working, but when i hit 40mph the voltage never i figure electrical, so i took the 2 leads of my multimeter and shorted them together and the TC locked right up. Ok so its not getting a signal from the ecm. so my plan is to check for a singal directly at the ecm and if there isnt one replace it. With the intermitent nature of the problem and how it worked fine for over an hour, it leads me to believe its the ecm thats screwed and not a wire. Anything else i should check?

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Old 07-25-2001, 08:26 PM
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When I encounter an intermittent I tend to suspect connectors or wiring.

If you had a scanner you could see if the ECM were sending the lockup commnad.

BTW, good job on the diagnostics.

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Old 07-25-2001, 10:42 PM
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I just tonight found out what was causing my intermittent problem of my TC unlocking at cruising speeds. Seems my TPS sensor was acting up. I believe it to have been sending a full throttle signal to the ECM when indeed it was only at partial throttle causing the TC to unlock. I swapped the throttle bodies between my two cars and it caused my other one to unlock at light thottle as the first one. Swappd in a new TPS sensor and it works good again. BTW both cars are 89's. My guess on the full throttle signal is just a guess but I do know that it WAS the root of my problem. Hope this helps.
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