Arrow PCM and Limp Mode

[Nambo]

First off I am not being Nancy negative by posting this, just trying to share my experience and hopefully the resolution with the Viper community.

Went to COTA this weekend and the car performed flawlessly with the Arrow PCM until halfway through the 5th session and then through the esse's, bam limp mode. Service electronic throttle control, and a few other codes pop up including low voltage. Thought it might be the battery or maybe due to the new pulley not able to hold the charge at continued high rpm. Turns out fuse 26 is blown (ASD) and it may be related to the rear O2 sensors. I am working with Mark to fix the issue and will post up what we find. I am just really lucky I guess...

[Steve M]

Sounds like you might have melted through an O2 sensor wire...I doubt it had anything to do with the PCM.

[Jack B]

That would be my g uess, if you changed headers, it is important to route the O2 cable safely. I put the whole cable in a radiant sleeve when I installed Balengers.

Sounds like you might have melted through an O2 sensor wire...I doubt it had anything to do with the PCM.

[FLATOUT]

Thanks for posting, it helps us all. Let us know if it's the O2 sensor wire melting or something else.

Andy

[ViperGeorge]

Which header are you using? You no doubt melted the rear O2 wires. Even though the Arrow PCM should not try to read the rear O2s it probably still activates the 12 volt heater wire. Melting the wires cause a short to ground resulting in a blown ASD and usually a bunch of codes. I'd suggest plugging the rear O2 bung and unplugging the rear O2s. In fact just unplug them and then replace ASD fuse. I would think this would get you running again.

[Nambo]

Which header are you using? You no doubt melted the rear O2 wires. Even though the Arrow PCM should not try to read the rear O2s it probably still activates the 12 volt heater wire. Melting the wires cause a short to ground resulting in a blown ASD and usually a bunch of codes. I'd suggest plugging the rear O2 bung and unplugging the rear O2s. In fact just unplug them and then replace ASD fuse. I would think this would get you running again.

I am running Belanger headers. I am going to unplug the O2 sensors and see if that solves the problem.

[Darius]

My car is stock and it's gone limp mode both times I've been on the track. I have to pull over, shut it off and wait a few minutes then restart. It doesn't like the rev's going up on downshift off throttle.

[FLATOUT]

My car is stock and it's gone limp mode both times I've been on the track. I have to pull over, shut it off and wait a few minutes then restart. It doesn't like the rev's going up on downshift off throttle.

First time I've heard of that happening.

[FLATOUT]

I am running Belanger headers. I am going to unplug the O2 sensors and see if that solves the problem.

Is there a nice aftermarket O2 wire loom shield or wrap we can use?

[Nambo]

Is there a nice aftermarket O2 wire loom shield or wrap we can use?

Sure seems like a necessary mod with the headers.

[FLATOUT]

Sure seems like a necessary mod with the headers.

Cheap and easy peace of mind for any aftermarket exhaust setup I would think.

[Jack B]

I used the 1-1/2" insulating sleeve. It comes in rolls and I believe it was made by DEI. One salvation was the temp drop with the single high flow Balenger cat.

Is there a nice aftermarket O2 wire loom shield or wrap we can use?

[FLATOUT]

I used the 1-1/2" insulating sleeve. It comes in rolls and I believe it was made by DEI. One salvation was the temp drop with the single high flow Balenger cat.

Good to know, thanks Jack!

[Nine Ball]

I used the 1-1/2" insulating sleeve. It comes in rolls and I believe it was made by DEI. One salvation was the temp drop with the single high flow Balenger cat.

I used the same stuff. They even make a version that has velcro to close it, so you can even install it while the O2's are still connected. I also cover my hydraulic line for the clutch slave cylinder in this stuff.

[BLUETA#1]

My car is stock and it's gone limp mode both times I've been on the track. I have to pull over, shut it off and wait a few minutes then restart. It doesn't like the rev's going up on downshift off throttle.

Are you heel-toeing to match the revs on the downshifts?

[Jack B]

For those that have not looked, there is a sheet
metal plate that shields the hyd clutch line. That is good, however, there are gaps where the hyd line is within two inches of the header. The sticky back radiant sheet barrier works nicely to deflect the direct radiant heat

I used the same stuff. They even make a version that has velcro to close it, so you can even install it while the O2's are still connected. I also cover my hydraulic line for the clutch slave cylinder in this stuff.

[Orange TA]

Just curious, how was your car dyno tuned if you have the Arrow PCM?

First off I am not being Nancy negative by posting this, just trying to share my experience and hopefully the resolution with the Viper community.

Went to COTA this weekend and the car performed flawlessly with the Arrow PCM until halfway through the 5th session and then through the esse's, bam limp mode. Service electronic throttle control, and a few other codes pop up including low voltage. Thought it might be the battery or maybe due to the new pulley not able to hold the charge at continued high rpm. Turns out fuse 26 is blown (ASD) and it may be related to the rear O2 sensors. I am working with Mark to fix the issue and will post up what we find. I am just really lucky I guess...

[Nambo]

Just curious, how was your car dyno tuned if you have the Arrow PCM?

Need to update my sig. Was Dyno tuned with the HP Tuner. Had a limp mode issue at COTA in December related to throttle tables. Switched over to the Arrow since I don't have easy access to a tuner that it trust.

[mjorgensen]

That would be my g uess, if you changed headers, it is important to route the O2 cable safely. I put the whole cable in a radiant sleeve when I installed Balengers.

Routed and sleeved like all our installations, the O2 sensor itself has more clearance than the other years so there must just be more overall heat, will get JD's car back again someday and see where exactly this happened. My guess is that this will be a possible issue with cars that see a lot of track time as we have not had any known issues until this one and we know JD can get after it on the track.

100_5946.jpg

[ViperGeorge]

I have seen quite a few tracked cars with headers melt their O2 wires. I've seen it on ARH and Bellangers. I regularly melted mine on my ACR with ARH headers even though they were wrapped with the DEI 1500 degree wrap. As long as you are running a race PCM (Mopar on the Gen 4 or Arrow on the Gen 5) you do not need the rear O2s at all. They can be unplugged or better yet removed and the bung plugged. The race PCM does not need them. The stock PCM uses them to determine CAT efficiency. However if you have to remove the race PCM and reinstall the stock PCM for emissions testing you will have to reinstall the rear O2s or you won't pass emission testing. If you have just unplugged them you can plug them back in but you need to make sure the wires didn't melt in the mean time.

As I stated above the race controllers still heat the O2 sensor even though they don't use it. When the wires melt, it shorts and usually blows the ASD fuse although sometimes it just throws codes and goes into limp mode. Not blowing the ASD fuse does not mean your wires aren't melted.

If the ASD fuse isn't blown and you restart car, it will sometimes come out of limp mode even with the wires melted. If the wires move a little and are no longer touching the car will run until the wires move again and touch and then back into limp mode you go.

I was going to experiment with some NASA insulation that had like a 500 degree thermal drop. It comes in sheets though and would have been somewhat of a pain to install. Once I discovered I could remove the rear O2s I did. The state where my cars are registered does not have emission testing.

[ViperGeorge]

I wonder if you could take a tube of some kind put it over the wires and then fill the tube with high temp silicone gasket stuff. Once it sets, remove the tube. If the wires did melt the silicone gasket stuff should prevent them from shorting and I would think the stuff would still be flexible. Maybe I will experiment with some old O2 sensors I have lying around.

[Nambo]

Rear O2 sensors disconnected, same outcome. Blown ASD fuse and went into limp mode.

[Dan Cragin]

Good thing you are blowing a fuse, just trace out that circuit, check the front O2 wires as well.

[Rapidrezults]

Rear O2 sensors disconnected, same outcome. Blown ASD fuse and went into limp mode.

Why don't you pop the stock PCM back in and see if the problem continues? If it does, take it to the dealer and let them trace it out.

[Nambo]

Why don't you pop the stock PCM back in and see if the problem continues? If it does, take it to the dealer and let them trace it out.

Those are the next steps, isolate front O2's then PCM.