Obd 337,157,543

[Mtn_Man]

94 Limited 4WD. Ok, changed the MAF (157) and the EGR Vacuum Regulator (337) and the codes persist. Cleared the codes with the reader, but didn't yank the batt cable I'll try that next. What else should I be looking for?

 

[MrShorty]

1st thing one usually looks at is which are the KOEO codes and which are CM codes (see my "notes on pulling EEC-IV codes" in the EEC-IV forum). Because KOEO codes are set with the engine off, they are almost always electrical faults, and are usually the preferred place to start. According to my code list, the 157 is the only one that cannot be a KOEO code.

KOEO 337: most KOEO 33x codes are trigger by a fault in the DPFE sensor circuit, and the DPFE sensor itself is often implicated. Probably a good place to start.

 

[Mtn_Man]

The DPFE was replaced a bout three years ago, but I have read a lot of bad about the quality of the aftermarket parts. Thought I was ahead of that game because the replacement was exactly like the orig - aluminum case and all. Guess I'll start back probing the sensors to see who has lost their mind. OBD II is sooooo much easier. (sigh) Thanks.