Q: I replaced pcm and now I'm getting code u0100 and p0700. Battery is new and not holding enough bolts. Something is draining it. Wh

asked by on March 26, 2017

Brand new pcm installed. Throwing codes u0100 and p0700. Battery is new also and not holding enough bolts. Something is draining battery why car is off. Car will start up fine but stalls out with those codes showing. Could the low voltage be why codes are thrown? Need help.
My car has an automatic transmission.

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To determine if the cause of those two codes is low voltage, I would simply fix the parasitic power draw first, reset the PCM (erase the codes) and see if the problem recurs. The cost to resolve such an electrical fault is in part made up of diagnostic time and, in part, the cost of materials or components, if the parasitic power draw is due to a failed electronic module, relay and so forth. If the electrical fault causing current to flow is pinpointed quickly and readily it should not be too costly. Basically, using the factory wiring diagram, a Mechanic would use an ammeter to test the circuit, segment by segment, until the fault is found. If you want these steps performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an electrical diagnostic and the responding certified mechanic will get this resolved for you.


Once the electrical problem is resolved, if the two codes recur, it would be important to know what codes, if any, existed prior to the PCM replacement and also of relevance in the diagnostic is why the PCM was replaced; they fail very rarely. Typically, Code U0100 involves either PCM or transmission control module failure. Interestingly, in your case, the additional code P0700 can set if the TCM itself has failed. Note that a bent or pushed out pin terminal or a bad ground to the PCM can cause U0100 to set. I would recommend first requesting the electrical diagnostic referred to above and during that, or at the conclusion of that, the two Codes will, of course, have to be diagnosed and the fault resolved as U0100 alone will definitely cause the car to stall. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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