QuestionHi,
Our car has 163,000 (mostly highway) miles and gets 30+ mpg. We have an intermitant problem that happens after smooth driving. At times it will seem to stumble and loose power. The tach drops slightly and then pops back up again. Feels as if someone has pulled the plug and plugs it back in repeatedly (quickly). There are times it runs great the whole trip, then other times it won't. We have replaced the fuel pump and filter, cap and rotor, plugs and wires, and also cleaned the PCV system. After many attempts, we finally got error codes via the key on-off method with the check engine light. The codes are in the order as follows: #12, #37, #21, #52 and finally #55. We hope this is an easy fix and appreciate your help. Mindy
AnswerHi Mindy,
The codes are helpful to me. The 12 codes means that the power to the engine controller has been disconnected recently. If you are not aware that the battery has been purposely disconnected in the past 50-100 on-off cycles than that is a code that may be relevant because if there were a loose battery clamp or loose or corroded ground clamp to the body, that might very well cause the repeated "pulled the plug" feeling. So check the clamps to the battery posts and also follow the 2 braided wires that are attached to the -post to find any connections that might be loose or corroded (one wire goes to a bolt on the rear of the engine the other to the inner fender shield on the left side of the engine comparment. I would loosen/remove the bolts and clean the interfaces of the connection points with emery paper or a file). Be careful when checking the + post clamp to not touch the wrench to any other metal object nearby; in fact it it better to disconnect the - post clamp entirely, then service the + post clamp, then reconnect the - post clamp.
The 21 and 52 codes refer to the heated oxygen sensor mounted on the exhaust manifold of the rear bank of cylinders. It either is worn out of has a damaged connector at its tip. I don't think it will cause the stumbling but may cause a loss of fuel efficiency and steady loss of power. So that would be worth replacing, or at least check the wires (gently) and the disconnect plug. You will need to use some penertrating oil on the threads a day before you try to change it and do the removal when the engine is cold. That way you are more likely to get it out easily and without doing damage to the threads. Be sure to use the anti-lock compound on the threads of the new sensor and use caution in handling the wires.
The 37 code may be a 'phantom' in that it refers to a transmission solenoid that isn't used with the 4 speed automatic (but is used with the 3 speed) so it is likely a false code.
So checking those first two items that are most likely to resolve the problem. Please let me know how it works out.
The 55 code means "end of readout". Be aware that unless the codes are erased (with a diagnostic readout box or by disconnecting the battery) that they will stick around in the memory for 50-100 key cycles after a fault is corrected before it self-erases the codes. So if the sensor was replaced and the codes not erased that would explain why you still have that code. And of course if you erase the codes by disconnecting the battery you will still have a 12 code for a while afterwards.
Roland
