Codes 42 and 54

[Jehu]

I used the paperclip jumper to read codes. It was easier than I expected.

I just got this truck. (1993 K1500, 5.7) It runs rough at high and low RPM. The first thing I did was replace the plugs, wires, cap and rotor. Not much improvement although the shape of the plugs indicated that it was due.

I checked timing. It was off about 4 deg. I set it to unplugged at 0 deg. (TDC). Plugged in, it checked at 20 deg adv at idle. I understand that to be correct. No difference in performance.

I shotgunned the MAP sensor and Engine Temp Sensor. Still no improvement.

I got those codes but I don't know if they're "leftover." Do codes reset in short time? If not, perhaps I need to reset and give it a couple days.

With codes 42 & 54, does anyone have any suggestions on what to try next?

 

[jkeaton]

Is the check engine light on? If not, disconnect the battery to clear the codes.

 

[Jehu]

Is the check engine light on? If not, disconnect the battery to clear the codes.

Thanks for the reply.

I assume that's a diagnostic strategy. That is, see if they come back shortly to make sure that they're legitimate. Is that the case?

 

[jkeaton]

Yes. Can't hurt to try.

 

[someotherguy]

Code 42 may be a leftover from having the timing wire disconnected. It should clear itself after a few run cycles. If not, there's definitely an issue with the ignition control circuit or the module itself. Sometimes the wires on the distributor that plug into the module can become brittle, so that's a place to check.

Code 54 is telling you that you have a fuel pump relay circuit problem (low voltage.) Considering the fuel pump relay grounds at the front of the intake either at or next to the thermostat housing, check all those grounds VERY closely, clean them up, repair as necessary. These grounds are very important.

Richard

 

[Jehu]

Code 42 may be a leftover from having the timing wire disconnected. It should clear itself after a few run cycles. If not, there's definitely an issue with the ignition control circuit or the module itself. Sometimes the wires on the distributor that plug into the module can become brittle, so that's a place to check.

Code 54 is telling you that you have a fuel pump relay circuit problem (low voltage.) Considering the fuel pump relay grounds at the front of the intake either at or next to the thermostat housing, check all those grounds VERY closely, clean them up, repair as necessary. These grounds are very important.

Richard

Can the fuel pump relay grounds cause rough running?