I have a 1989 Pickup with a 22RE and manual transmission. The CEL came on briefly several times within a 10 mile drive this morning so I went to run the codes and got the following:

14, 21, 42, 43, and 51

And holy cow, I was not expecting 5 different codes. I'm honestly not sure where to start, I've read up a little bit and know that I need to closely look over grounds/connectors. However, after searching the codes each one lists the ECU as a possible fault.

The truck drives ok, but I do get a hesitation/miss when im at about 1-50% throttle. Other than that I don't notice any problems with drive-ability and the CEL does not stay on.

Any advice on where to start would be appreciated.

Thank you!

 

Just to update, cleared all codes and drove back home from work. Threw codes 21 and 42 pretty immediately. Which I find interesting as code 42 is for the vehicle speed sensor. Now please correct me if I'm wrong but it is my understanding that the speed sensor is not present in my vehicle as my speedometer is cable driven? Or am I totally off base here?

edit: after some digging it sounds like the mechanical cable drives a speed sensor in the gauge cluster. And my cable broke a week or so ago. Is it possible that this is causing a cascade effect on the entire EFI system and the reason for multiple different codes?

 

Likely a short to the transmission on the oxygen sensor wire, or just old stored codes. (This causes blown fuses or voltage drops, which can falsely trigger codes due to partial resets of the ECU)

You can check in the FSM for the procedure to verify the other codes.

Good job on the research. The cable driven speedometer does output the digital speed signal to the ECU.

 

Thanks for the reply! I looked over the O2 sensor wiring and it appears to be ok, it's a denso sensor that I installed about a year ago to replace the original sensor. I just replaced the speedometer cable as well and reset the ECU. I'm going to drive around a bit and see if any of the codes come back. If they do I'll start troubleshooting with the FSM and let you guys know what I find.

Thanks again!!

 

I think I found the culprit, and I sure feel silly. When I checked the O2 sensor I just checked the connection and glanced at the wiring from the sensor to the connector. Well shoot, I looked 6 inches upstream of the connector and found that the wiring was resting on the exhaust. This had melted the insulation on the wiring and has been causing a short. Once it's repaired I'll update but I expect that this is the culprit.