So as many of you know I did a automatic to 5spd swap in my 94 360. Everything went together well, but I've been having trouble with my PCM communication with my O2 sensor. I noticed this problem when I was running my 360 with the 318 manual pcm I removed from my parts truck, before I oredered a 5.9 manual pcm. The fist thing I did was change my o2 sensor out with a brand new denso unit, thinking my origional o2 finally died. Same issue. Once the pcm grounds the ASD relay to send itself into closed loop one the truck is warmed up the CEL illuminates. Now I've gone ahead and tested my harness for continuity.

Pin 2 on o2 side to pin 41 pcm side is the sensor signal, it reads good.

Pin 1 o2 side to pin 4 pcm is sensor ground, that checks out.

12v to asd relay checks out

ASD to pin 4 o2 checks out

Pin 57 Pcm to control side of ASD relay checks out

The harness I have is a 95 from a 5.2 half ton, which means it is wired only for a single O2 sensor. But the cel still illuminated with the 5.2 pcm.

Now since I'm usi a 5.9 HD pcm, does it call for 2 O2 sensors like all the FSM's state? Nowhere else on the internet have I found that the 94-95 HD 5.9 and 5.2 trucks have 2 o2 sensors, one in each bank. It seems like that's only on the v10? Or do all HD federal emision trucks have 2 pre cat o2 sensors?

Even so, if that's the problem with my 5.9 HD pcm, that doesn't explain why I had the same code 21 with my 5.2 half ton pcm.

Anyone who can confirm that the 94-95 5.9 gas 2500-3500 trucks have 1 or 2 pre cat o2 sensors please let me know.

 

 

I know the HD engines had some differences, they should be detailed, sorta... in the FSM.

The Code 21 indicates the sensor is shorted to voltage, OR, stays at center..... Do you have a scanner that will let you read data, and see what the sensor is actually doing?

 

There should be a separate entry for the HD version of the engine in the wiring diagrams.

 

 

I do not have a scanner that can read the data. That is the only v8 entry in the 95 FSM. The other two are the v6 which shows only one sensor and the v10 with is basically the same thing as the v8 drawings.

 

Ok, check out this page for some troubleshooting tips. Unfortunately, OBDI doesn't specify WHICH sensor is causing the trouble, if there is more than one.

Also, it appears that the HD PCM IS going to expect a left, and right, O2 sensor. Looks like the left side one goes to pin 23 in the PCM connector. Is there anything there?

 

There isn't nothing for the left o2 sensor as i am using the 5.2 manual 1/2 ton harness. I just wasn't for sure or not whether the HD version of the V8 had a second one, because I could not find info on that anywhere else online except for the service manual.

 

In the 94 manual, section 14-32, figure 2 shows a wiring diagram for the HD PCM, and clearly shows two O2 sensors. (left and right)

I can't find any info on whether or not dodge has any additional codes for the HD engines. (which would have been nice.)

If there isn't a wire for the left side O2 sensor, I suspect you could fool the pcm, simply by feeding the signal from the one that is there, to both pins....... Would it solve your problem? That, I don't know.

 

Was there a HD 5.2 in 94-5? According to my 96 fsm it was only the 5.9 that was HD. Not sure if the vin sequence is the same but the 8th digit is for the engine. Z is the standard and 5 is HD. If you swapped in HD pcm you will need the harness for it also due to the extra 02.