Hi All - My CEL has been coming on and I had it checked at the mechanic and here is where things are at ...

1995 Ram 2500 - V10 engine

My CEL started coming on after driving about 2 miles and stays on. When I shut the truck off and start it up again, the CEL is off, but again, comes on after driving about 2 miles.

The mechanic checked this out and said this was caused by a slight miss in one of the cylinders and by the evap canister. He said it was nothing to worry about, since the miss was very slight and that if I wanted him to, he would check into the evap system and little more, but realistically, I had nothing to worry about, especially since the 95' isn't checked for emissions during inspection.

I want to get this fixed because with the CEL coming on, I keep worrying about something eventually getting damaged - probably just me over reacting, but not sure where to start. All my research says to start with replacing the canister or check for leaks in the hoses, but right now the temperature here has been in the teens, so it's a little too cold to spend time playing with this, so for now, is there a way I can quickly bypass this, that is, without causing any damage?

 

Nope. Need to find the problem, and fix it.

I am actually surprised you are getting misfire codes. My 98 had a dead miss on one cylinder, due to the plug wire being burnt in half....... and the PCM never set a misfire code.....

What codes are you actually getting?

 

Normally I would check this out myself, but my 95' doesn't have the connector to use a scanner to get a code, which is why I took it to the mechanic. He told me he'd have to do it the old fashion way and about 20 minutes or so later told me there was a slight misfile with a reading like 16000, but said that was nothing unless it was a lot higher.

As far as the evap canister, he just said that was also causing a problem, although if I wanted to get the CEL fixed, he'd have to pursue this further to pinpoint the actual cause. He didn't give me much more to go on.

I did go under the truck today and noticed the back part of the canister where the hosed attached, the very tip where it extends out, that part spins around and I'm not sure if it is supposed to do that. Gonna try to get under there again and take a picture.

 

Should be able to do the key trick to get codes. Cycle the ignition on-off-on-off-on, and on the last 'on', watch the check engine lite. It will blink codes. Likely start with 12, and it will end with 55.

 

Didn't know that would work on the 95', so here is what I got.

12 - 21 - 21 - 55

Did it twice and the same thing - got a 21 twice both times. If my search was correct, 21 indicates the following: 21** Problem w/ oxygen sensor signal circuit. Sensor voltage to computer not fluctuating. (** means it will trip the Check Engine Light)

Now this is different then what the mechanic told me. I did do some research and it all seems to first point to a CEL and evap canister problem, but now with a code, it may also be the sensor voltage to computer not fluctuating. I need to see the location and how many sensors there are.

But with that said, I do have a buzzing noise in the back of the truck, which I traced to one of the cats (my truck has 2 cats going into one muffler) and the outer cat is the one that is buzzing or rattling, so I am assuming something inside must be loose. Could that be adding to the equation?

 

The O2 sensor code tends to indicate a failed sensor. The rattling cat likely means the cat is bad. The honeycomb inside is breaking down. (and that's what is rattling around.) At this point, I wouldn't even worry about the EVAP stuff, unless it sets another code. Crawl under the truck, and see how many O2 sensors you have. Might be two, might only be one. I suspect the latter.

 

The V10 has two O2 sensors, one in each down pipe. That's before the cat so if that's defective it doesn't cause any CEL. The full description from the FSM is:
02S Stays at Center - Neither rich or lean condition detected from the oxygen sensor input. If equipped with dual 02S sensors, the DRB scan tool will specify left or right sensor.
-Or-
02S Shorted to Voltage - Oxygen sensor input voltage maintained above the normal operating range. If equipped with dual 02S sensors, the DRB scan tool will specify left or right sensor.

The first is the sensor not following the rich/lean cycle from the fuel quantity adjustments. As the O2 sensor needs a certain temperature to work it could be just the heater which you can test with an ohmmeter across the white wires (sub 10 ohms).

The second one often happens when the heater voltage gets onto the sensor wires which can happen when the sensor goes bad but also have a look at the wiring.

As a side note the truck has a diag connector just not OBD2. It's a 6 pin connector near the PCM with 2 of the pin oriented 90 degrees from the other.

 

Will do and update - haven't yet because since your post, we've gotten a little over a foot of snow and it's been in the low teens to single digits - too cold and snowy to roll under the truck right now. I may have a chance mid-week. We'll see,

 

Yup, found this in the manual "The 8.0L V-10 engine uses two oxygen sensors, one in each exhaust down pipe." ...

But with that said, you mentioned these wouldn't trigger a CEL, which then brings me back to what the mechanic said, in that is was probably caused by the evac canister.

The question now is, why did I get the following code when turning the ignition key and the following description?

12 - 21 - 21 - 55

Did it twice and the same thing - got a 21 twice both times. If my research was correct, 21 indicates the following: 21** Problem w/ oxygen sensor signal circuit. Sensor voltage to computer not fluctuating. (** means it will trip the Check Engine Light).

 

Signal not fluctuating means the sensor has failed. If they are original, replace them both. NTK or Denso sensors only please.