Q: Car starts, then stalls in one second.

asked by on

My mom recently got her oil changed and had been driving for a while until suddenly one night her car would turn over and stall immediately. You push the button to start the car, and it'll start, but then die immediately. I tried revving the engine in the second that it's on, and it revvs high but still dies just as fast. There were even times it would die, then start revving again for a second, and die again. My OBD2 device gave me a P0685 code saying the following:

Powertrain - Computer and Auxiliary Outputs - ISO/SAE Controlled ECM/PCM Power Relay Control Circuit/Open

The dealer is trying to sell her on a mass airflow sensor and battery replacement for $600 at the moment. It seems like a computer issue to me, not a sensor. If you could give me some trustworthy advice on how to proceed, I'd greatly appreciate it.

My car has 35000 miles.
My car has an automatic transmission.

Hi there. This can be a computer issue, but from the codes and the issue it sounds more like a voltage problem. If there is low voltage from a bad battery or a bad connection then the vehicle will act like this due to a communication problem. I have also seen the push button ignition switch fail on this vehicle and cause this. I always start by load testing the battery and checking all of the ground connection as these are the most common causes of this on your vehicle. If you find you are needing a second opinion on the work, or help with definitively diagnosing the issue, a certified technician from YourMechanic can come to your home or office and make repairs.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car starts, then stalls in one second.

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: The vehicle keeps turning off while driving. Hummer H3

Hello - the first task is to determine what problem codes are being set here. This will guide diagnosis, and tell whether it's a fuel supply issue (fuse, fuel pump relay, or fuel pump itself), or possibly an electrical sensor...

Q: AC compressor only engages around 40% of the time

This is likely due to a faulty thermostat sensor which is responsible for controlling the temperature at which the AC compressor comes on. To determine this will require a series of tests. I would recommend having an expert from YourMechanic...

Q: Car accelerates very slow when it hits 20 mph and neutral shift on dash starts to blink.

Either the transmission has thrust bearings or bushings that are worn causing the internal parts to go out of balance or there is an issue with the fluid is low causing the gears to slip. If the fluid is full...

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...