ABS/ Brake light on/ Cruise control doesn't work

[Blueox01]

Thinking the rear ABS speed sensor is also used for setting cruise, can't see it connected in wiring diagrams, must be in PCM, am I correct in thinking these are related problems?

[dripley]

Thats my understanding. Speed signal goes to the abs then to the pcm and then the ecm and cruise is set. Too many computers in that party for me. But if I am wrong someone will straghten us both out.

[Blueox01]

Well, my cruise won't set and ABS/brake lights are on. But speedo ins't haywire.

Edited June 12, 2019 by Blueox01

[Mopar1973Man]

25 minutes ago, Blueox01 said:

Well, my cruise won't set and ABS/brake lights are on.

 

Still there is a speed signal error. truthfully there is no real path of the speed signal. This why the CCD bus is different. The ABS just broadcasts the speed signal for any computer that is listening. So the ECM, PCM and Cluster all listen when ABS announces. Now if there is a CCD Bus issue like a P1698 or P1694 code that signal is not getting to the PCM or ECM. Gauge Cluster is a separate module and also controls the bus bias voltage for the CCD bus.

[dripley]

Thanks for clarifying that. My education continues.

[Blueox01]

4 hours ago, Mopar1973Man said:

 

Still there is a speed signal error. truthfully there is no real path of the speed signal. This why the CCD bus is different. The ABS just broadcasts the speed signal for any computer that is listening. So the ECM, PCM and Cluster all listen when ABS announces. Now if there is a CCD Bus issue like a P1698 or P1694 code that signal is not getting to the PCM or ECM. Gauge Cluster is a separate module and also controls the bus bias voltage for the CCD bus.

'splian that again.

[Mopar1973Man]

2 hours ago, Blueox01 said:

'splian that again.

 

Ok. 

 

First off the ABS module is reporting ABS and BRAKE light. This is a speed sensor error. There is 3 speed sensors 2 sensors in the front axle and 1 sensor in the rear axle. There is a mismatch of speed between the 3 sensors. All 3 sensors MUST report the same speed or the ABS and BRAKE lights are turned on. 

 

As for the ABS module it will broadcast it speed signal on the CCD network. Any module that is listening can receive speed information from the ABS module. ECM uses the speed signal for cancelling grid heaters. PCM uses speed signal for cruise control and transmission information. The gauge cluster uses it for the speedometer. 

 

Now if there is a CCD network error P1698 or P1694 then the information is not getting to either the ECM or PCM. The gauge cluster might still function find because it just listens for speed signal. 

 

 Just for information purpose the PCM is the master computer that creates the CCD network and the gauge cluster is what sets the voltage bias for the CCD network. If there is a P1698 or P1694 code then either the ECM or PCM is not hearing the CCD network.

[Blueox01]

Well , I replaced rear ABS/Speed sensor ABS light still on and cruise doesn't work. Not worried about the ABS just getting cruise to work, according to the 2001 manual diesel " Diesel With Manual Trans The speed control system is fully electronically controlled by the Engine Control Module (ECM). A cable and a vacuum controlled servo are not used if the vehicle is equipped with a manual transmission and a diesel engine. This is a servo less system.The controls consist of two steering wheel mounted switches. The switches are labeled: ON/OFF, RES/ACCEL, SET, COAST, and CANCEL.The system is designed to operate at speeds above 30 mph (50 km/h)." But this is not true on my truck, Mine DOES have a vacuum controlled servo, My model year is a 2001 and came with a 6 speed.  Sure wish I was smart enough to figure this out, supposed to leave tomorrow for CA. I do have vacuum to the servo and my cruise light comes on just won't SET/RESUME or ACCEL

[Blueox01]

Never mind Cruise is working, not sure what fixed it, put some dielectric grease on plug, works now.

[JAG1]

 I'm glad you found it....Did the ABS light go out as well? Which plug if you don't mind my asking.

[Blueox01]

No ABS light still on, Plug to Cruise servo

[JAG1]

Just for the heck of it check those fuses in the PDC.... Especially those with the window. It is very hard to see the burned link in those, but a magnifying glass and small flashlight helps. Really need to pull and test with OHM meter is how I found a bad one and got my ABS light to go out. 

Edited June 14, 2019 by JAG1

[Mopar1973Man]

9 minutes ago, JAG1 said:

Really need to pull and test with OHM meter is how I found a bad one and got my ABS light to go out. 

 

Like myself I done all the ohm testing and wire testing everything showed good. It was the tone rings failed in the front bearings. That's why I own 3 sets of ABS front sensors right now.

[JAG1]

Do you remember which brand sensor finally showed up as reliable?

[Mopar1973Man]

11 minutes ago, JAG1 said:

Do you remember which brand sensor finally showed up as reliable?

 

All of the sensors. Sensor wasn't the issue it was the wheel bearings. The tone wheel was damaged. After replacing the unit bearings lights went off in 100 feet. I basically wasted nearly $300 on front axle speed sensors to find out the tone wheels were bad.

[Dieselfuture]

On 6/14/2019 at 9:25 AM, Mopar1973Man said:

 

Like myself I done all the ohm testing and wire testing everything showed good. It was the tone rings failed in the front bearings. That's why I own 3 sets of ABS front sensors right now.

I only got one set of sensors ha ha, learning from the best.

[JAG1]

 

9 hours ago, Dieselfuture said:

I only got one set of sensors ha ha, learning from the best.

Mike's way too sensortive about his truck..... Sorry...... delete that

Edited June 16, 2019 by JAG1

[Mopar1973Man]

 

2 minutes ago, JAG1 said:

Mike's way too sensortive about his truck..... Sorry...... delete that