50GT

Hey guys my check engine light stated flashing this week. I haven’t noticed a difference in performance at all. I pulled the codes today and got code 87 with the key on and engine off. I know that code 87 means fuel pump primary circuit failure. With the key on engine running I got code 91. I know that code 91 means left HEGO system indicates system lean. Could this be caused by a bad O2 sensor on the left side? Would that cause a problem with the fuel pump or could my fuel pump be getting ready to crap out, causing a problem with the left side O2 sensor? The funny thing is that I'm not getting a code 41 for the right side HEGO indicating lean. Any help you guys can give would be much appreciated! Thanks again!

Joel5.0

Switch O2 sensors from sides.... if code 41 shows afterward, that O2 (now on the RH side) needs a replacement.

50GT

Ok thanks joel I'll try that. Would a bad O2 sensor cause the code 87 or would that be a different issue?

Joel5.0

Different issue.... as soon as you ID if the O2 needs to be replaced..... clear codes and then retest for code 87, which means there could be a problem in the FP relay coil circuit.

50GT

Thanks Joel the problem seems to be fixed! I had an extra O2 sensor lying around, pulled out the old one and put the new one in and cleared the codes. I drove the car around all day and the check engine light didn’t flash one time. When I got home I checked to see if any codes had been stored. To my amazement no codes, not even code 87. Weird but it even idles better...lol. Thanks again for the help!