what is Pin #42 output on the ECM

[Rich Hoefer]

I just took delivery of my 03 Dodge quad cab 2 wheel drive on Thursday, and installed the Pac Brake on her on Friday (01/31/03). The Pac Brake does not operate. My question is, can some one tell me what kind of signal the ECM sends out to the brake unit when it is supposed to engage the exhaust brake.

I have checked and rechecked my wiring, which is quite simple and straight forward, It appears to me that when the throttle is released and goes to an idle, The system completes the ground circut, which tells the ECM to engage the exhaust brake.

What is the value (voltage) that is sent through the single wire that goes from Pin #42 of the ECM to the Pac Brake Relay.

 

[Casey Balvert]

Pin 42 I believe goes to ground. With the exhaust brake switch in the OFF position you should have 12 volts. My Jacobs brake also uses pin 39 which tells the ECM that the exhaust brake is activated. I think. You might want to recheck your instructions again. Hope this helps. Casey

 

[Rich Hoefer]

Thanks Casey. On the Pac Brake instructions, Pin 39 is used to go from pin #39 to a a clutch switch, then to the shifter lever switch and then to ground, so from what you say, it is just a continuation of the ground through pin 42 back to the brake relay.

Im a bit afraid to ground that wire to see if that makes the brake actuate in the event it is a low voltage output from the ECM.

 

[dmurdock]

Rich, call PacBrake. I called them about the same question (ecm hookup) when installing mine. The tech's know their stuff.

 

[Rich Hoefer]

Casey, Dmurdock

I found the problem with my Pac Brake.

The gearshift mounted switch is defective, At least i think it is. On installation the instructions call for the wires to be hooked as follows. Green to ground, Black to Pac Brake wire harness, this is the wire that connects to pin #39 in the ECM, and white wire to a keyed hot power source.

The power source wire is for powering the little green light in the switch when the Pac Brake is in engaged mode. For some reason, when my switch power wire is connected to key hot power, it renders my Pac Brake inoperatable. After I disconnected the power wire the brake performs great. I will contact my dealer as to the switch problem.

Thanks for the replies, guys.

 

[jelag]

As Rich mentioned.....



Some of the gear shift lever switches were shipped without a diode that will make the light work... . and allow the exhaust brake to work.....



If the switch is on and the brake won't function, disconnect the lead to 12V. and see if that solves the problem... .



PacBrake will replace the switch.....



Jim