3.8L Codes

Hello. I'm brand new to the forum.

I'm trying to help my mom get her 1993 Buick Regal GS 3.8L repaired. I suspected it needed the fuel pump relaced, but it appears my diagnosis was not correct. The mechanic says it is throwing codes 18,17,72,43,39, and 63. I don't know if there is a particular order. 63 indicates a problem with the cruise control. I'm not real concerned about that. 18 and 17 indicate a problem with the crank position sensor and 72 and 43 indicate a possible problem with the electronic ignition. (I think I've got all this straight.) Code 39, as I understand, is related to the torque converter and could be anything from a faulty sensor to major transmission trouble.

I can't decide what to do. The mechanic wants the OK for me to spend 500 bucks to replace the crank position sensor and the electronic ignition. I haven't called him on it yet, but doesn't it seem a little odd to change them both initially? Looks to me like you could change the crank position sensor and go from there. I know that you can take the igntion module and have it tested. The idea of changing both parts initially makes me not want to trust this guy.

Furthermore, I can't decide if 500 dollars to get the engine running perfectly is worth it if the transmission is about to go. I haven't seen a car yet with 130K+ miles that needed a cheap transmission repair. Should I try to get to the bottom of code 39 first, or do you think this code is sympathetic? Does $500.00 seem too steep to replace the crank position sensor and the ignition module?

Thanks very much for any assistance,
Brian

The CPS is a relatively inexpensive part although you need to remove the harmonic balancer to change it. The ignition module costs about $120 and can be changed by removing the coils and a few bolts. $500 seems a bit high to do this although he may be including a rediagnosis of the problems in the price. Once you have these two items completed disconnect the battery and clear the codes to see what happens. It is possible that none of the codes will reappear but if they do then work on them one at a time. Finally, the code 39 may go away when you clear the codes. If not it is probably related to the TCC solenoid which can be a hastle but won't ruin the transmission. Try these items and see what happens.

Well - I called the mechanic this morning and told him I really didn't want to change the ignition module and the CPS at the same time. He told me he really felt like the problem was the igntion module and wanted to start there. I gave him a reluctant OK..

He called back just a little while ago to tell me that he had cleared the codes and driven the car and cleared the codes several times. (No parts have been swapped at this point.) He said the only code he can get now is 22, which indicates a problem with the TPS. He said that could be the cause of everything, so I told him to go ahead and replace it.

I've spent my lunch hour looking at posts that talk about the TPS, and I believe I understand what it is. Sounds like a variable resistor in series with a 5 volt pullup. He told me all he could get out of it was .25V. I hope he's smart enough to take a resistance reading before swapping it out. Knowing what I know now, it seems like maybe it's just shorted to ground. Or, I suppose a short could happen internally on the TPS... I don't know how these normally go bad, although one poster on this forum said it was pretty rare.

We'll see what happens.

The tps will often fail for various reasons not one specific cause. Some just wear out over time. It is like a rheostat that sends varying inputs to the computer based on throttle position to tell the computer the need for more fuel. This mechanic sounds like he knows what he is talking about and that he is not going to do anything that you don't authorize in advance. I think he will fix the problem for you relatively inexpensively.

The mechanic just called to say that swapping the TPS sensor did the trick. He's driven the car a good bit and it hasn't thrown a single code.

In the future, If the check engine light is on, I'll be diligent to figure out what the codes are indicating instead of making a self diagnosis based on performance.

Thanks for all the replies. Hope this helps someone else some day.

Thanks,
Brian