Ram1

Ok, to start I am having problems with my PacBrake and I was talking to Pacbrake and the service tech said to disconnect my batterys for about 10 mins to reset my computer. (he thinks my idle is not right, causing my pacbrake to turn on and off real quick at idle)

So, I go out and unhook my batterys for about 15 mins. After that I take a test drive to warm her up again. No luck. The brake still go on and off over and over at idle. Then I noticed that all of my presets on my radio were still set and the old P-Codes are still reading. So, I disconnect the batterys again. This time for 2 hours. Still the radio is still set and the P-Codes are there. The only thing that does not stay set is the time on the raido.

How in the heck do I reset the computer? Is there a battery backup for the raido stations?

I don't know if I am resetting the computer or not now.


I would like my pacbrake to work soon cause I have to be up in Berrien Springs, MI. with the Newmar company for a video shoot of my truck pulling their trailers on Monday for a TV show.

Thanks again, Greg

TonyB

Thei may sound silly: pull both negative leads. If you pull one pos & one neg, the truck still has power.

phox_mulder

The codes won't reset by disconnecting the batteries.

All the computer modules have backup batteries.

Only way to clear the codes is with a code reader.


phox

Smkndzl

the CM848 does not have a back up battery. but no you cant get rid of the code by disconnecting the batteries.

Ram1

I just found out you can't erase the codes by taking the leads off.

I took it to a guy that worked at Dodge and he has a reader and erased the codes for me.

As for resetting the computer he took the neg cable and touched the pos side of the battery while the pos cable was still on to reset the computer. That took care of the PacBrake. So I thought until I got about 3 miles away from his house the Pac started to act up once again. It was working just fine until then.

I guess I will have to call the Pac company in the morning to see what I can look for next.

Smkndzl

well that is certainly a good way to fry a good ECM , I have seen tech. fry ECM by disconnecting alternator cables and accidently touching the positive cable to a ground before disconnecting batteries. I am betting your Pacbrake problem has nothing to do with the ECM either.

CRXsi

Actually the battery cable method is safe...only one step left out. Make sure that since there are 2 batteries that you completely disconnect one of them first! After there is only one battery disconnected then you can remove the last battery's negative clamp and proceed to touch it to the positive terminal. This acts as a way to force a reset of the circuitry inside the computer. IF BOTH BATTERY'S ARE HOOKED UP WHILE DOING THIS DAMAGE WILL OCCUR! It is a technique used by many new cars to reset strange glitches from weird multiplex problems to guages that act up once in a while to driveability issues that aren't constant. Like I said only attempt this if the first battery is completely disconnected first. By touching the negative to the positive there will not be a short circuit because there is no ground path between the body and the battery but it does take all voltage out of capacitors and other items in the circuity of the various computers that are designed to retain memory after battery disconnect.

Ram1

CRXsi

Good Lord! We didn't unhook the 2nd battery!

The truck seems to act fine right now except the Pac is still not right. I may try it out again but I WILL unhook th 2nd battery this time.

Thanks for the heads up!

Ram1

JohnCA58, Any idea what would cause the Pac to act like it is?

CRXsi

Just as a side note...I haven't looked at a wiring diagram to see if there is a solenoid or relay that isolates one of the batteries if the key is not turned on but I suspect there isn't so I would play it safe by disconnecting one of the batteries first before attempting. You would know by know if it fried anything but I wouldn't attempt it a second time without isolating it to one battery. Also there should be no arcing or sparking when doing this as the ground between the battery and body is no longer connected. If you get any arcing or sparking then the 2nd battery hasn't been disconnected.

Ram1

CRXsi, Thanks

It did spark up the first time I tried it. So far the truck runs and acts fine and has not thrown out any codes.

I have yet to try it again today but I will after I have my coffee

bigblock2stroke

Faulty wiring to either the ECM or the solenoid that activates the brake when you let off the accelerator.

However, I think your pacbrake uses compressed air instead of vaccuum but the wiring to the relay should be similar.


With engine idling, wiggle the wires for the brake both at the ecm and relay to see if you can get it to act up.

Ram1

bigblock2stroke, Thanks I've tried that. I even have a spare relay and that is not the problem either. I have been beating my head to get it working.

I just tried to reset the computer again and it still acts up at idle....On/off On/off...etc...

Luckly I didn't have to go up to MI lastnight. The film company had to put it off for now. So, I can now work on this problem today again.

Now I am going to call PacBrake and see what we can do now.