Code 542

[kd7kmp]

I recently experienced a moderate drop in fuel economy. I decided to pull the codes to see if anything was up. The only code I got was 542. This code doesn't make sense to me as the car starts and runs fine. I have pulled the codes on previous occasions and this one has never come up. Any ideas? Thanks.

Kevin

 

[SolidState]

bad oxygen sensors will cause a 542

 

[SW SHO]

Bad 02 sensors can be telling of decreased gas miliage. The 542 is an fuel pump issue? What kind of decrease are you experiencing?

 

[kd7kmp]

SolidState: The O2 sensors are only about 1000 miles old. I don't believe they would cause a 542. 542 has to do with an open or shorted circuit with the fuel pump. Thanks for the input, though.

SW SHO: I have not figured the actual drop, but I don't get as much out of a tank between fill-ups. I will have to monitor the actual numbers for a couple tanks. Thanks.

Kevin

 

[Markus]

SolidState: The O2 sensors are only about 1000 miles old. I don't believe they would cause a 542. 542 has to do with an open or shorted circuit with the fuel pump. Thanks for the input, though.

SW SHO: I have not figured the actual drop, but I don't get as much out of a tank between fill-ups. I will have to monitor the actual numbers for a couple tanks. Thanks.

Kevin

Bad O2 sensors will trigger 542/543 codes. Don't ask me why, but they will. It's simply the way the EEC works. That being said, I've never seen a bad O2 sensor triggering ONLY 542/543. Usually there will be a 17x code with the 542/543 codes.