1993 Accord TCU help?
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1993 Accord TCU help?
I have a 93 Accord that the D4 light came on. I thought I fixed it by disconnecting the battery and resetting the TCU. This lasted about a month, then I couldn’t reset it again. I took the TCU apart and found a bad resistor and 2 bad capacitors, which I replaced all 5 capacitors and both resistors with new ones found on EBay. It still has the same issue, just a steady D4 along with whatever gear you place it in. There aren’t any codes when jumping the test lead. I don’t know if I could have damaged the board somehow during replacement. My solder joints look good. Or could there be another issue someplace else? I did notice that it can be shifted out of park without applying the brake, as long as the key is in the run position. I can’t say for sure how long it has been like this, just thought it may help diagnose. Can a dealer bench test the TCU for me?
Thanks
Thanks
MM Gruppe B
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From: 94577/Gaillimh
Re: 1993 Accord TCU help?
Check that the memory fuse is still good. If it is blown this will not allow any codes to be stored for later retrieval. You can also try retrieving codes while the car is running by jumpering the blue two wire connector and watching the D4/S or CEL lamp for any codes.
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Re: 1993 Accord TCU help?
I’m not convinced it is time for another TCU just yet. I hate to spend the money without being sure. Has anyone else repaired the resistors and caps to find out an unknown issue with the TCU? Does anyone know where to check for power at the plug?
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Re: 1993 Accord TCU help?
I checked the junkyards. Locally there aren’t any available and they don’t seem to want to venture out on their network. The money isn’t the issue. If there are any junkyard units available, it will be very likely they are bad or well on their way to be, due to age. I would like to be sure before I buy from a rebuilder.
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Re: 1993 Accord TCU help?
I checked the junkyards. Locally there aren’t any available and they don’t seem to want to venture out on their network. The money isn’t the issue. If there are any junkyard units available, it will be very likely they are bad or well on their way to be, due to age. I would like to be sure before I buy from a rebuilder.
I had this exact issue with my 92 (two leaking capacitors, 1 burned resistor) - ended up buying a used (tested) TCU from Ebay for $65 and the problem went away right after install.
Most sellers on Ebay have 30, 60, or even 90 day return policies.
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Re: 1993 Accord TCU help?
I replaced the TCU with a remanufactured unit. The D4 light now starts to flash after around 30 seconds of idling. The other issue is it won’t shift out of park while the engine is running. It will shift out of park if the key is in the ignition position, engine off. This would rule out the brake light switch and the interlock solenoid. Once again there are no codes stored. Where do I go now?
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From: 94577/Gaillimh
Re: 1993 Accord TCU help?
Missed this. For the original problem, the following is to check. With the new TCU the wiring was disturbed and the 'new' TCU may not be registering the issue correctly. Drive the car for a few minutes over 30MPH to see if it resets to steady on or an actual code.
With the ignition in II(ON) backprobe terminal A8 on the TCU and ground.
Is there voltage?
Yes. Check the BLU/RED wire to the gauge cluster for a short. Repair
No. Backprobe A17(TCU) and ground for voltage with the gear selector in any position other than D4.
Is there voltage?
No. Check for short to ground on the LT GRN/BLK wire. If wire is fine, replace AT gear position indicator.
Yes. Replace the TCU,
With the ignition in II(ON) backprobe terminal A8 on the TCU and ground.
Is there voltage?
Yes. Check the BLU/RED wire to the gauge cluster for a short. Repair
No. Backprobe A17(TCU) and ground for voltage with the gear selector in any position other than D4.
Is there voltage?
No. Check for short to ground on the LT GRN/BLK wire. If wire is fine, replace AT gear position indicator.
Yes. Replace the TCU,
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Re: 1993 Accord TCU help?
Mike, I cleaned the ignition switch contacts. I don’t believe that was the problem, but after a few start cycles, I can get it out of park. I took it for a ride and it held on to first gear for a very long time before it went into second. It had to coast down hill to get into third and as soon as throttle was applied, it would shift up and down irratically. I nursed it back home in First and second. I jumped the service connector and got a code 15 on the cel side. Low ignition output. The car runs fine and the speedo works as it should. I also took the Vss apart and cleaned it. Same result. I will back check the wiring again tomorrow. I did check for voltage at A8 and cleaned the gear selector switch. I will follow through with the rest of your suggestions tomorrow. Thanks for the help.
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From: 94577/Gaillimh
Re: 1993 Accord TCU help?
I'll dig up diagnostics on the code 15 if I can for the 93, It's probably the same as the 94-97s.
Engine performance does greatly affect transmission shift characteristics.
Engine performance does greatly affect transmission shift characteristics.
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Re: 1993 Accord TCU help?
I sent the rebuilt TCU back and requested a refund. It tested bad. I am having my doubts as to if it was rebuilt at all. I have another one on the way. It should arrive by Wednesday. I’ll let you know what happens.
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mikeconover
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Nov 23, 2017 09:37 AM