Pacbrake Quit Working

[RagingCajun]

Hi Guys,

I have a question and the statement above my be wrong. The pacbrake still works but not with me using the normal switch, see I did some trouble the other day and I can jump out the solenoid valve and the pac will close.

What is the two wires come or going from the PCM I know these are the two wires which closes the circuit from the switch inside the cab. I did check and I have a code P-0477 show and can not reset this from turning on/off on/off on/off the ignition switch.

Is this the reason that the pacbrake is not working? I'm 600 miles from home and need my exhaust brake back!



I know someone my have the answer

 

[JLandry]

I'm not real familiar with 2003 and up models, but I believe there's a relay which controls the exhaust brake. If that relay is malfunctioning, it would trigger the P0477 trouble code.



My best guess is this relay would be inside the IPM (Integrated Power Module) on the left front fender. If you can locate it, try swapping this relay for another one of the same size but on a non-essential circuit like the windshield wipers, etc. If that does the trick, you should be able to buy a replacement relay from a good auto parts store or any Dodge dealer.



If that doesn't do it, then post back here and we'll try to help you with more suggestions.



BTW, you'll need a code scanner to clear the trouble code which has been set.



Good luck,



John L.

 

[Bob V]

The relay for the Pac brake is not in the pcm, most likely it is on the compressor. Remember, the switch in the cab controls the ground side of the control circuit.

 

[RagingCajun]

Yes, I was able to jump out the solenoid at the compressor and it works fine. Is there any reason you have to go through the control circuit? It would be very easy just to run 24v to the solenoid.

Thanks again and I'll look for the other relay.

 

[Bob V]

The contol circuit is low watage from the ECU.

 

[RagingCajun]

So what is it I have to do? I think there is one wire plug into 75 and the other 47, I think! Does anyone know how I get I get that voltage to come out of the ECU?
Also can I run 12 volts to the solenoid and bypass the ECU?

 

[jelag]

First one side of your switch should be grounded and the other side should go to one of the pins on the ECM...

Second... the ground side of the relay control coil goes to the other pin on the ECM... .

What we've found is that if you haven't taken the connector off the ECM to make sure that the pins fully locked into the connector that is the first place I would look... .

We try and tell all our customers to ignore the PacBrake suggestion to just push the pins into the connector... we've had too many that didn't lock in and later would not make a good connection... pull the connector and make sure that the pins have snapped into place...

If after you've check the above feel free to either call us at 800. 445. 4696 M-F 730 - 500 and speak to Jack for help or give PacBrake tech support a call at their 800#

I hope your wrong about plugging into 75 and 47 both sound wrong to me... I'm sorry that I'm sitting in a motel this evening and don't have access to the company computer...

THE ECU does not supply voltage to the control circuit of the relay... instead its the ground side that it works on...

What the ECM does is see your grounded switch and when the brake needs to come on it grounds the relay with 12 supplied to the other side of the coil by the battery connection...

Hope this helps... . BTW I'm sitting here in a motel... and will come back to this thread later...

 

[Pacbrake]

try resetting the Throttle postion sensor

DODGE 2003 AND NEWER THROTTLE POSITION SENSOR RESETTING



PLEASE READ THOROUGHLY BEFORE STARTING RESET PROCEEDURE



Step1. Turn the key to the RUN position (but not started)



Step2. Slowly depress the Throttle pedal all the way to the floor, slowly release to idle (remove your foot from the pedal @ idle), slowly depress to the floor and back to idle 2 more time so you have gone 3 times in each direction.



Step3. After the 3rd time to idle, Turn the key off.



Step4. Start the truck and allow it to idle for 3-5 minutes.

(DO NOT TOUCH THE THROTTLE )



Step5. After it has idled for 3-5 min. Turn the truck off, then restart it and go for a test drive.



Note it may be necessary to do this more than one time. To get it reset.

 

[RagingCajun]

Jim,
Thanks for the help, I just crawled under the truck and found the white wire (39) not seated in place. Used an pair of needle nose pliers to give it a good push and works like it use too.

The two wires are black at pin 42 and white at 39 just for future reference for anyone.