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89 Prelude - S3 light flashing


altaguy

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I have an 89 Prelude with automatic trans. Recently the S3 light started to flash and the auto trans started to miss 2nd gear on up and downshifts. Now, when I start out in the morning, things go normally for a while and then after the car is warmed up, it starts forgetting it has 2nd gear again and the S3 light starts to flash.

 

I have done some research [manual and Net] and this indicates transmission issues. Some info. I found seems to indicate resetting the TCU by disonnecting the battery sometimes works. Others say change the trans fluid with Honda fluid. Others suggest read the TCU codes by jumping a cable under the dash.

 

I have these questions:

1. Can the TCU be reset by a simple battery cable disconnect on a 89 Prelude? If so, how long should it be disconnected?

2. Should I first attempt to read the TCU codes before resetting it? If so, does anyone know where I can get info on the Net as to what the flashing code numbers mean?

3. What should I do if the TCU is bad? Junkyard replacement? rebuilts?

4. Any other ideas?

 

Thanks in advance for any thoughts.

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I have an 89 Prelude with automatic trans. Recently the S3 light started to flash and the auto trans started to miss 2nd gear on up and downshifts. Now, when I start out in the morning, things go normally for a while and then after the car is warmed up, it starts forgetting it has 2nd gear again and the S3 light starts to flash.

 

I have done some research [manual and Net] and this indicates transmission issues. Some info. I found seems to indicate resetting the TCU by disonnecting the battery sometimes works. Others say change the trans fluid with Honda fluid. Others suggest read the TCU codes by jumping a cable under the dash.

 

I have these questions:

1. Can the TCU be reset by a simple battery cable disconnect on a 89 Prelude? If so, how long should it be disconnected?

2. Should I first attempt to read the TCU codes before resetting it? If so, does anyone know where I can get info on the Net as to what the flashing code numbers mean?

3. What should I do if the TCU is bad? Junkyard replacement? rebuilts?

4. Any other ideas?

 

Thanks in advance for any thoughts.

1. Yes, usually a 10 second disconnect will clear the codes.

2. Absolutely, if somethings wrong you want to fix it. I have nothing for the 2nd part of your question.

3. Always the best bet is to buy a new, OEM replacement. Unfortunately not everybody can afford that, so you go with whichever option is best for you. Remember that typically you get what you pay for.

4. I don't mess with Autos much, so no.

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I bought a TCU for my girlfirends car on ebay. 3 year warantee. Only cost $138 shipped.

 

The only thing is you have to return your old one for warantee and good feedback, kinda a exchange deal.

 

Immediately after putting in the new one all problems disappeared.

 

Resetting first is a good start. Her car had a LED window on the TCU for reading codes.

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Ludedude25:

We also read the LED light codes that were 7 & 8, which indicate trouble with the 2 separate shift solenoids on the tranny. Do you recall the LED codes that your car was giving? I gotta think it would be rare that BOTH solenoids would go at the same time. Could this point to the TCU box? Dunno, guess I will have to take it to a Honda dealer to let them troubleshoot from here. Thanks for your suggestions.

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Ludedude25:

We also read the LED light codes that were 7 & 8, which indicate trouble with the 2 separate shift solenoids on the tranny. Do you recall the LED codes that your car was giving? I gotta think it would be rare that BOTH solenoids would go at the same time. Could this point to the TCU box? Dunno, guess I will have to take it to a Honda dealer to let them troubleshoot from here. Thanks for your suggestions.

Rare perhaps, but certainly not impossible.

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