Skip the auto shop - Our mechanics make house calls

Q: Warning lights come on after battery replacement

asked by on

After changing the battery, all was going well. The next day when I started my car, almost all of the warning lights came on (for ex: ECP, ABS, brake, engine, steering). The speedometer didn’t work either. However, the car is running just fine, fortunately. These things do work: windows, wipers & pump, lights, stereo, etc. The dealership technicians told me that there is no communication with any of the modules and that they need to be replaced. They aren’t able to explain why the car is still working and they can’t tell me what is wrong. Before I give them $5k, please give me your diagnosis of the problem, your advice, and if there’s a way I can fix this. Thanks.

A: Hello. It sounds like the PCM (powertrain c...

Hello. It sounds like the PCM (powertrain control module) and the BCM (body control module) have malfunctioned because of a shortage in the battery system. This could have happened when the battery failed, was removed, or installed. One explanation for why the car is still working is that the PCM and the BCM has not completely failed, which is allowing it to still function. The only way to repair this problem is to replace and reprogram the PCM and the BCM.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Drove in manual on accident on freeway for 30 mins.

Hello. It is likely that one of the lower gears were damaged when the transmission was stuck in manual mode. I'm guessing that the gear that it drove was first gear until you got to your destination. Driving in first...

Q: Steering wheel locked

This is a pretty common problem on Ford trucks. Typically, you can get the steering wheel to unlock by turning the wheel side to side while also turning the key forward. If this doesn't work you likely need to replace...

Q: engine cam broke

The Chevy Monte Carlo was only equipped with the 3.1 and 3.4 liter engines in 1996. The 3.8 was used for a lot of GM vehicles and come with different accessories and wiring connections. You would need to verify...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...