Mach 1 Sudden Loss & Regain of Power while Driving - I believe electrical (PCM power)


May 26, 2018
Austin, TX
Recently my 03 Mach 1 has had a Sudden Loss & Regain of Power while Driving. This has happened 4 times now on 4 daily driving events. Here are the details (and most common observations):

- Started the car and started to drive, then POW!!!, loss of power, all cluster gauges go dead, Theft and ABS light on/flashing, but car still running (rough). This results in a momentary loss of acceleration.
- I think all of these have happened with 30 seconds of starting the car
- I turn off the car fairly quickly (needed to stop first)
- Try to start the car again and nothing. No dash indicator lights, wont start (like no power from the battery to the PCM). I don't hear the CCRM turn the fuel pump on either.
- Wait for a while say 1 minute, try to start and it starts, things seem fine
- Cluster needles all reset (go from all left, to all right and back). Much like when the pcm has been fully drained (like resetting kam memory)
- This happened today when I started it and turned on the headlights and A/C (but did not have those things turned on with the other events)
- Did a code scan and got the following code which reflects a bad battery

What I think is happening:
- PCM is dropping below 12 volts long enough to lose KAM memory
- This would cause the cluster gauges to die and loss of engine power as the PCM does not send instructions to the engine (I am assuming power loss to the pcm and not power surge)

What I did find today.
- Went to Autozone to get the battery and alternator checked
- They found the battery was bad, so we replaced it
- Then tested the alternator after replacing the battery and it was good, no need to change it


Do you think this headache is gone with the bad battery being replaced? Can a bad battery cause an issue like this?

Things to consider if the issue is still there:
- I cleaned all the grounds on the car within the last year for another reason
- I had tested moving wires around with the lights on (car off) like the battery connections, ground strap, etc to see if the lights dip. Nothing.
- Could be the alternator (but they said it was OK)
- Could be a fusible link
- Could be other wiring
- Perhaps the PCM, but feels unlikely to me since it runs outside of these events

I am hoping it is gone with the battery change. The only way I know to try to test it at the moment is just start things and turn lots of things on and see what happens. I want to be careful as I don't want the pcm to fry if it keeps happening.

Thanks for any advice
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Active Member
Apr 8, 2017
If the battery had a cell opening up inside that could have been the problem. Drive it under same circumstances a few times close to home to see if it still does it.


May 26, 2018
Austin, TX
Did a KAM reset and relearn process, then took it for a cautious ride. Then added lights and A/C. So far so good. Will take it slow again later tonight and then one more time tomorrow. Hopefully things are good.



SN Certified Technician
Aug 14, 2009
Houston Texas
Can a bad battery cause an issue like this?
Absolutely! A bad battery can (and does) cause the alternator to drop out. Why? Because the battery is used to excite the alternator's field coil. Without a working battery the alternator can not respond up increases in requested load.

Frequently one of the symptoms of a bad battery is a motor that suddenly stops for no apparent reason but is able to be restarted easily. The usual cause is an "open" within one of the battery cells. Or a battery that is soooooooo weak that it's voltage drops too low when there's a large increase in system current (remember that the battery has to soak up any increase while the alternator's voltage regulator is increasing the strength of the field coil).

Howto perform charging system voltage drop test
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Reactions: MattMan02GT


May 26, 2018
Austin, TX
Thanks for that explanation!!! I normally just went by the battery is for starting and the alternator runs the car. But clearly there is much more to it.

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