Skip the auto shop - Our mechanics make house calls

Q: Battery connected backwards and won't start

asked by on

The battery in my car was connected backwards. I replaced the blown relays that are in the fuse box. There is full power to all acc, but the car just won’t crank and it won’t turn over. So I jump-started the starter and it’s working, but it’s not getting the signal. Everything else in the car works fine, as far as I can tell. What should I do next to find the solution?

A: Hello. Most of the time this is caused by a...

Hello. Most of the time this is caused by a failed main fuse. If the fuses have been replaced then it is more than likely a bad module. In most cases the engine control module will fail when the battery is jumped backwards.

The computer needs to be scanned with a scan tool to see if it is powering up and seeing sensor signals. If you need to have this done, consider YourMechanic, as a certified mechanic can come to your home to diagnose your starting problem. An accurate repair can be made one the problem has been pinpointed.

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: Car start problems, diesel leak

If liquid fuel can leak from the line, air can definitely be introduced into the line during operation. This air in the line can throw off calculations for the air/fuel mixture and cause the engine to stall or run very...

Q: Hard to shift, shaky clutch, started smoking

Hi there, thanks for writing in. I'd be happy to help. The leak is most likely from the clutch slave cylinder. Look in the clutch master cylinder reservoir and see if it is low or empty. If it is, then...

Q: The fuel pump and dashboard lights indicator shut off after the 4 wires in the neutral safety switch shorted out

It sounds like you may some blown fuses from that shorted switch. Inspect the fuses and replace as necessary. An electrical wiring diagram and a digital volt/ohm meter will be needed for further diagnosis if replacing the fuses does not...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.