On my 99 F-150 4X4 the ABS light is on, so.

  • 1999 FORD F-150
  • 98,500 MILES
On my 99 f150 4x4 the abs light is on, so brought it into a shop an had the code read. Front left sensor needed to be replaced so replaced it and still have the abs light lit up. I have checked all fuses and disconnected the battery multiple times and have drove it at least 40 miles since replacing front left sensor. What else could it be that would be throwing a code for front left? Any input appreciated.
Tuesday, December 11th, 2012 AT 5:40 PM

1 Reply

First of all, do you know it's the same code?

Second, who replaced the sensor, you or a mechanic? If you did, did you erase the code? If it wasn't erased, it will still be there because the computer will just think it's an intermittent problem that currently isn't acting up.

Third, fault codes never say to replace parts. They only indicate the circuit that needs further diagnosis. There was only about a 50 percent chance the sensor was the cause of the code. You also have to look at the wiring and connector terminals.

Fourth, you didn't specify what the code actually said. There are codes that will set due to an incomplete electrical circuit, as in a break in one of the wires going to the sensor, a corroded electrical terminal, or a break in the wire inside the sensor. There are entirely different codes for a mechanical problem, as in a cracked toothed tone ring. Electrically the circuit can be intact but it won't generate a signal. You can get a potential clue by when the code sets and the warning light turns on. With an electrical problem, the light will come on right after the seven-second self test / bulb test is done after turning on the ignition switch. With a mechanical problem, the light won't turn on until the vehicle is in motion.

Fifth, and this is the hardest one to understand, all fault codes set only if a long list of conditions is met, and some of those conditions are that certain other codes aren't already in memory. That's because the computer compares many things to each other to know when something is wrong. There can be an entirely different second problem that won't set a code until the first problem is fixed. That is more likely to happen when the first problem is ignored for weeks or months. It happens especially often on GM vehicles and is very frustrating for mechanics who rely on those codes to provide accurate estimates for cost of repair, and it's frustrating for owners who have to be told more repairs than expected are needed.
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Tuesday, December 11th, 2012 AT 10:08 PM

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