QuestionQUESTION: Hi HT. Our 99 Elantra only very rarely, if ever, shifts into OD out on the open road. The OD switch IS engaged. Even in-town, sometimes it has trouble shifting between gears and revs high when it should be down-shifting. The Check Engine light is on.
We took it to a place where the non-hyundai expert stuck an analyzer on it. I did not make note of the actual codes, but the text said "Manufacturer Controlled Computer (and) Outputs".
Is this an owner-replaceable part? I located the MMC (behind and under the ashtray in center console). Is the MMC the same as the TCM?
We would be grateful for any insight or suggestions.
ANSWER: "Manufacturer Controlled Computer (and) Outputs" indicates that the diagnostic trouble code is manufacturer-specific and the code reader doesn't know what it means. Without knowing the actual code, I won't be able to provide much help.
You'll need to read both the engine and transmission diagnostic trouble codes. Not sure where you went originally, but AAMCO and AutoZone have advertised they'll do this for free. Be sure to get the actual code numbers and follow up with them here. I'll tell you what they mean and advise on how to proceed.
---------- FOLLOW-UP ----------
QUESTION: Alrighty, Autozone hooked up their analyzer and we got the following codes:
P0722 "Output Speed Sensor circuit no signal" and
P1624 "Manufacturer ____ code" (I think it said manufacturer control code)
The Autozone tech went on his computer and looked up these codes. For the P0722, it indicated Transmission Pulse Generator, with 3 possible causes: Open or short circuit, poor electrical connection, or failed pulse generator. For the P1624 it indicated anti-theft alarm.
Interestingly, the check engine light is no longer illuminated.
AnswerP0722 is exactly what they say. P1624 is simply an indicator in the ECM that the check engine lamp was requested by the TCM.
Replace your pulse generators (input and output speed sensors bundled together). When done, do not reattach the electrical connector to the tang. Just connect it and let it lay on top of the transmission. This will most likely solve the issue.
For your reference, I recommend you read technical service bulletin 03-40-022. You can do so at www.hmaservice.com. You'll need to register for a free account, and the site requires Internet Explorer. The step I've recommended above addresses the first (and by far most frequent) in a list of things that may be causing your problem.
