What is causing my Service Engine Soon light to stay on?

10

Asked by Jan 02, 2014 at 07:17 AM about the 2002 Ford Mustang GT Convertible

Question type: Maintenance & Repair

Since owning the car, (April 2012), I've had a problem with the Service Engine
Soon light staying on. The diagnosis came back that the hot air sensor was faulty.
I've had it changed as well as a couple of coils that went bad. I bought a set of
headers, because of an exhaust leak, (headers were rotted) and still the light
stays on and says it's the hot air sensor.

9 Answers

223,315

Do you have the factory catalytic convertors on? The O2 sensors will throw a code if not.

1 out of 1 people think this is helpful.
465

Some systems require a 'reset' for the ecu. Most of the time disconnecting the battery for more than 10 minutes will do the trick. Some of the mustang forums suggest: 1) disconnect the battery for 15 minutes, 2) reconnect the battery and start the vehicle, 3) let idle until warm, 4) turn A/C on (if equipped) and idle for 5 minutes, 5) drive the vehicle for 10 miles. If that doesn't work have the dealer reset it. Depending on the year there are different reset methods. If it still stays on run the codes again.

8 out of 8 people think this is helpful.
10

I have duel catalytic converters. As for the reset, the battery has been disconnected a couple of times. When I go to the dealer they would want to change the hot air oxygen sensor, (That's what shows up on the computer), but that has already been changed.

465

If resetting the ECU has no effect, then Tom may be right. But if the O2 sensors have been replaced and it still codes then look for the obvious like a frayed/shorted wire or a bad connector. You say you had the headers replaced. Were they replaced with stock or aftermarket parts? Has anyone done a test for a shorted or broken wires?

2 out of 2 people think this is helpful.
10

The headers are after market, purchased a couple of months ago, but I've been having the service light problem since I had the car.

465

I really don't know what to tell you to do. Something is definately amiss. Usually if you fix the code and the problem persisits it is something in the wiring either broken (open circuit) or shorting to ground. I have heard of problems as strange as being in the dashboard itself. Either way it is going to take time and patience to narrow down what circuit is causing the problem. There is a cheap fix, and I shutter to even suggest it. Just remove the bulb.

2 out of 2 people think this is helpful.
10

Yeah I suggested that but my mechanic advised against it. However to me for the light to be always on is the same as it never being able to come on. Either way it is not telling me anything.

1 out of 1 people think this is helpful.
20

I HAVE a 1997 gt mustang and my engine light came on had the mechanic check the code and it was just the gas cap so I had to buy a new one and the light went off

2 out of 2 people think this is helpful.

Will it pass inspection in new jersey if light stays on?

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