Stumped! 97 3500 cruise control. - Competition Diesel.Com

95cummins5.9 · 02-06-2018, 12:50 PM

I have a problem, cannot get the little green light to come on for the cruise switch. I have eliminated the clock spring via continuity test, eliminated the switch itself via ohm test, the vss is good on ohm test, I have my 5 volts to the vss. Swapped switches on the wheel with a known green light working switch.. continuity tested the brake switch and have swapped it also with known working part.

My yellow wire with the red stripe never has any power under any circumstances, not at the brake switch not at the clock spring. No where. Is it possible this truck has a pcm from something without cruise? Help please haha.

b.lee · 02-06-2018, 02:42 PM

Check all the wires connecting to the battery terminals.

I had some corrosion (not very much) on the all the wires going to the batteries on my old 96, snipped them all off clean and re-attached them, then my cruise control started working again.

Just something to check out if you havent already

95cummins5.9 · 02-06-2018, 04:02 PM

New terminals with new ends, new batteries.

95cummins5.9 · 02-06-2018, 04:22 PM

Guessing the pcm is the problem, everything else checks out. What pcm's interchange guys?

jedeka · 02-06-2018, 06:26 PM

I just removed a working PCM out of a 96 with auto tranny.

odieub · 02-06-2018, 07:06 PM

Believe 97 is obd2 . And only 97 will interchange with itself. Maybe wrong have been before.

GAmes · 02-06-2018, 07:39 PM

Did you test the servo?

The engine must be started and running for the
following voltage tests.
(1) Start engine.
(2) Disconnect 4-way electrical connector at servo
(3) Turn speed control switch to ON position.
(4) Check for battery voltage at pin-3 of wiring
harness 4-way connector (Fig. 3). This is the 12 volt
feed from the stoplamp switch. When the brake pedal
is depressed, voltage should not be present at pin-3.
If voltage is not present with brake pedal not
depressed, check for continuity between servo and
stop lamp switch. Also check stop lamp switch
adjustment. Refer to Group 5, Brakes for procedures.
(5) Connect a small gauge jumper wire between
the disconnected servo harness 4-way connector
pin-3, and pin-3 on the servo. Check for battery voltage
at pins-1, 2 and 4 of the servo. If battery voltage
is not at these pins, replace the servo.
(6) Turn ignition switch to OFF position. Check for
continuity between disconnected servo harness
4-way connector pin-4 and a good ground. There
should be continuity. I f not OK, repair open circuit to
ground as required

I found, due to the location of the servo, to do step 5 is much easier using a pigtail cut off a donor vehicle. They are easy to find, common to Durangos and minivans. A '96 PCM with the same type transmission will interchange.

DTC code 34 is for Speed Control Solenoid Circuits - An open or shorted condition detected in the
Speed Control vacuum or vent solenoid circuits and won't give you a check engine light.

95cummins5.9 · 02-06-2018, 07:49 PM

I would of went on to those steps Gary, but I cannot get the switch to turn on as needed in step 3.
I pulled the cruise switch completely apart to verify the green indicator light was good. Is the servo part of the circuit to power the switch?( Manual at shop)
When I pulled apart the servo I continuity tested the coils inside and verified free moving valves and no holes in the diaphragm.

Thanks for taking time to reply everyone.

jasonc · 02-06-2018, 07:58 PM

What is the source for the yellow-red wire? Maybe back track that to the source.

GAmes · 02-06-2018, 08:20 PM

The source for YL/RD is PCM pin C137 speed control feed. I'm also seeing a RD/LG from PCM C32 speed control switch signal that appears to have power. Did you check it?

95cummins5.9 · 02-06-2018, 09:03 PM

Yes the red and green stripe should power the cruise switch from pcm, I typed that wrong in the original post i just noticed. With my power prob hooked up it shows a blip of non ground very brief and intermittent, with harnesses hooked up. Guess I'll pull it off and see if that wire is still ground tomorrow, while it's disconnected..
I wonder if supplying 5v to that wire would jump around the ecm?

GAmes · 02-07-2018, 08:06 AM

From the diagram I think (not positive though) that the YL/RD is an input wire to the PCM, specifically speed control switch position. The RD/LG is the output to the speed control vent solenoid. There is also another output, TN/RD that goes to direct to the servo speed control vacuum solenoid, but I doubt that is the culprit. There are two connectors between the PCM and the switch, C126 and C133 which might be the problem. I have a diagnostics manual that might tell us what the voltage should be, but it is in the shop. I'll post after I get a chance to look at it.

CorneliusRox · 02-07-2018, 08:34 AM

Make sure your all your three servo pins are at 41 Ohms to the ground pin.
Also, you can supply the 12V power and bypass the PCM, this will give you your light and power the servo, it just wont pulse the vacuum. I'd think hooking up a relay to ignition to power the system might be a cheaper route than a new PCM.

Two other things:
1) Look for any corrosion under the drivers side battery. Not just on the servo, but in general, that whole area. Check continuity if you can.
2) Those clock springs are SOBs. If you have another truck lying around, I'd suggest trying it. On my truck, it passed continuity, so I replaced the servo, switch, and checked everything else. Then it turns out that two of the wires in the clock spring had wore through the insulation and were touching.

GAmes · 02-07-2018, 10:00 AM

The YL/RD is in fact the 12 volt power supply from C11, which is a different number than the FSM shows. That is a grey plug. According to the diagnostics manual the PCM is faulty if, (all things being met) in order,
1. s/c switch voltage below 1.0 (connected)
2. voltage in the s/c switch does not go to 5.0 volts when disconnected
3. resistance between the s/c signal circuit (pin 3, WT) and sensor ground ground circuit (pin 2, DB/) is above 5 ohms. That is measured at the switch connector.
4. With the PCM disconnected (check connectors for cleanliness and damage) check resistance on the PCM between pins C32 and A4 (black plug). If the resistance is above 5.0 ohms the PCM is faulty. Note; The diagram shows the plugs and their pin locations. It is not clear (to me at least) if it is the pin holes in the plugs where the resistance is checked or the PCM itself.

Hope that wasn't clear as mud. I'd just post the wire diagram if I could.

CorneliusRox · 02-07-2018, 10:33 AM

That old PCM service manual is such crap though. It drives me crazy.

95cummins5.9 · 02-07-2018, 12:49 PM

Thanks everyone! I pushed it to the side. Will prob get too it Friday. Will post my findings.

jlbayes · 02-07-2018, 01:55 PM

Quote:

Originally Posted by odieub

Believe 97 is obd2 . And only 97 will interchange with itself. Maybe wrong have been before.

96 was start of obd II. So 96 & 97 will work as long as the transmission matches.

95cummins5.9 · 02-12-2018, 11:02 AM

Ok guys, the servo tested 84.4 ohms on all but one pin which had 42.4 ohm. Assuming that points to a bad servo..

I did end up jumping 12 volts to the yellow and red wire, and that does give me my light, but under no circumstances does it ever have power, running, key on not running etc , without the jumper power wire.
With it jumped I do get power to the servo plug, it has good ground, continuity etc.

The pcm test Gary put up rules out the pcm ,from what I can tell.

Anything else beside swapping clock springs and or giving direct power? Im not following that it won't pulse the vacuum? Could you explain a little more? Thank for taking the time to help fellas.

02-06-2018, 12:50 PM	#1
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	Stumped! 97 3500 cruise control. I have a problem, cannot get the little green light to come on for the cruise switch. I have eliminated the clock spring via continuity test, eliminated the switch itself via ohm test, the vss is good on ohm test, I have my 5 volts to the vss. Swapped switches on the wheel with a known green light working switch.. continuity tested the brake switch and have swapped it also with known working part. My yellow wire with the red stripe never has any power under any circumstances, not at the brake switch not at the clock spring. No where. Is it possible this truck has a pcm from something without cruise? Help please haha.

02-06-2018, 02:42 PM	#2
b.lee Name: b.lee Title: 6 in a row, makes it go. Status: Not Here Join Date: Oct 2008 Location: Southeast, MI Member`s Gallery Posts: 107	Check all the wires connecting to the battery terminals. I had some corrosion (not very much) on the all the wires going to the batteries on my old 96, snipped them all off clean and re-attached them, then my cruise control started working again. Just something to check out if you havent already __________________ 2012 2500 Cummins 4x4 - Mega Laramie, Auto, EFI Live

02-06-2018, 06:26 PM	#5
jedeka Name: jedeka Title: Too Much Time Status: Not Here Join Date: Oct 2009 Location: Boone, Iowa Member`s Gallery Posts: 1,413	I just removed a working PCM out of a 96 with auto tranny. __________________ 1996 Dodge Ram 2500 4x4, 5 spd. 4.88 gears, 2.5" turbo, Smokem inj, 5000 rpm springs, NV271, South Bend dd clutch, 33x12.50-15 STS tires, 6 inch stack, custom valve springs 2005 3500 4x4 dually, auto, KORE leveling coils, 19.5 wheels, Smarty Jr

02-06-2018, 07:06 PM	#6
odieub Name: odieub Title: Too Much Time Status: Not Here Join Date: Nov 2007 Location: Leitchfield, KY Member`s Gallery Posts: 923	Believe 97 is obd2 . And only 97 will interchange with itself. Maybe wrong have been before. __________________ 95 1500 rc sb 2wd p7100 24v auto, ats 5 star, suncoast kit, dtt billit input, sperico, fun tire eater. In pieces 95 2500 2wd rclb nv5600 500k 5x.012 ddp 887 pump, #11 plate hx35/40-14cm 16 3500 4wd aisin cclb dually flatbed, toy hauler

02-06-2018, 07:39 PM	#7
GAmes Name: GAmes Title: Retired Apache pilot Status: Not Here Join Date: Jun 2012 Location: Killeen, TX Member`s Gallery Posts: 271	Did you test the servo? The engine must be started and running for the following voltage tests. (1) Start engine. (2) Disconnect 4-way electrical connector at servo (3) Turn speed control switch to ON position. (4) Check for battery voltage at pin-3 of wiring harness 4-way connector (Fig. 3). This is the 12 volt feed from the stoplamp switch. When the brake pedal is depressed, voltage should not be present at pin-3. If voltage is not present with brake pedal not depressed, check for continuity between servo and stop lamp switch. Also check stop lamp switch adjustment. Refer to Group 5, Brakes for procedures. (5) Connect a small gauge jumper wire between the disconnected servo harness 4-way connector pin-3, and pin-3 on the servo. Check for battery voltage at pins-1, 2 and 4 of the servo. If battery voltage is not at these pins, replace the servo. (6) Turn ignition switch to OFF position. Check for continuity between disconnected servo harness 4-way connector pin-4 and a good ground. There should be continuity. I f not OK, repair open circuit to ground as required I found, due to the location of the servo, to do step 5 is much easier using a pigtail cut off a donor vehicle. They are easy to find, common to Durangos and minivans. A '96 PCM with the same type transmission will interchange. DTC code 34 is for Speed Control Solenoid Circuits - An open or shorted condition detected in the Speed Control vacuum or vent solenoid circuits and won't give you a check engine light. __________________ '97 Dodge 3500, G56, slightly bombed, A million+ miles, started 2nd million on 8/24/13 Now past 1.3 million and going strong. Last edited by GAmes; 02-06-2018 at 07:45 PM.

02-06-2018, 04:02 PM	#3
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	New terminals with new ends, new batteries.

02-06-2018, 04:22 PM	#4
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	Guessing the pcm is the problem, everything else checks out. What pcm's interchange guys?

02-06-2018, 07:49 PM	#8
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	I would of went on to those steps Gary, but I cannot get the switch to turn on as needed in step 3. I pulled the cruise switch completely apart to verify the green indicator light was good. Is the servo part of the circuit to power the switch?( Manual at shop) When I pulled apart the servo I continuity tested the coils inside and verified free moving valves and no holes in the diaphragm. Thanks for taking time to reply everyone.

02-06-2018, 07:58 PM	#9
jasonc Name: jasonc Title: Too Much Time Status: Not Here Join Date: Nov 2009 Member`s Gallery Posts: 4,412	What is the source for the yellow-red wire? Maybe back track that to the source.

02-06-2018, 08:20 PM	#10
GAmes Name: GAmes Title: Retired Apache pilot Status: Not Here Join Date: Jun 2012 Location: Killeen, TX Member`s Gallery Posts: 271	The source for YL/RD is PCM pin C137 speed control feed. I'm also seeing a RD/LG from PCM C32 speed control switch signal that appears to have power. Did you check it? __________________ '97 Dodge 3500, G56, slightly bombed, A million+ miles, started 2nd million on 8/24/13 Now past 1.3 million and going strong.

02-06-2018, 09:03 PM	#11
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	Yes the red and green stripe should power the cruise switch from pcm, I typed that wrong in the original post i just noticed. With my power prob hooked up it shows a blip of non ground very brief and intermittent, with harnesses hooked up. Guess I'll pull it off and see if that wire is still ground tomorrow, while it's disconnected.. I wonder if supplying 5v to that wire would jump around the ecm?

02-07-2018, 08:06 AM	#12
GAmes Name: GAmes Title: Retired Apache pilot Status: Not Here Join Date: Jun 2012 Location: Killeen, TX Member`s Gallery Posts: 271	From the diagram I think (not positive though) that the YL/RD is an input wire to the PCM, specifically speed control switch position. The RD/LG is the output to the speed control vent solenoid. There is also another output, TN/RD that goes to direct to the servo speed control vacuum solenoid, but I doubt that is the culprit. There are two connectors between the PCM and the switch, C126 and C133 which might be the problem. I have a diagnostics manual that might tell us what the voltage should be, but it is in the shop. I'll post after I get a chance to look at it. __________________ '97 Dodge 3500, G56, slightly bombed, A million+ miles, started 2nd million on 8/24/13 Now past 1.3 million and going strong.

02-07-2018, 08:34 AM	#13
CorneliusRox Name: CorneliusRox Title: Seasoned Rookie Status: Not Here Join Date: Dec 2012 Location: Detroit, MI Member`s Gallery Posts: 4,154	Make sure your all your three servo pins are at 41 Ohms to the ground pin. Also, you can supply the 12V power and bypass the PCM, this will give you your light and power the servo, it just wont pulse the vacuum. I'd think hooking up a relay to ignition to power the system might be a cheaper route than a new PCM. Two other things: 1) Look for any corrosion under the drivers side battery. Not just on the servo, but in general, that whole area. Check continuity if you can. 2) Those clock springs are SOBs. If you have another truck lying around, I'd suggest trying it. On my truck, it passed continuity, so I replaced the servo, switch, and checked everything else. Then it turns out that two of the wires in the clock spring had wore through the insulation and were touching. __________________ Corey - BSME '21 Tesla Model 3 Perf '22 DMax AT4 2500

02-07-2018, 10:00 AM	#14
GAmes Name: GAmes Title: Retired Apache pilot Status: Not Here Join Date: Jun 2012 Location: Killeen, TX Member`s Gallery Posts: 271	The YL/RD is in fact the 12 volt power supply from C11, which is a different number than the FSM shows. That is a grey plug. According to the diagnostics manual the PCM is faulty if, (all things being met) in order, 1. s/c switch voltage below 1.0 (connected) 2. voltage in the s/c switch does not go to 5.0 volts when disconnected 3. resistance between the s/c signal circuit (pin 3, WT) and sensor ground ground circuit (pin 2, DB/) is above 5 ohms. That is measured at the switch connector. 4. With the PCM disconnected (check connectors for cleanliness and damage) check resistance on the PCM between pins C32 and A4 (black plug). If the resistance is above 5.0 ohms the PCM is faulty. Note; The diagram shows the plugs and their pin locations. It is not clear (to me at least) if it is the pin holes in the plugs where the resistance is checked or the PCM itself. Hope that wasn't clear as mud. I'd just post the wire diagram if I could. __________________ '97 Dodge 3500, G56, slightly bombed, A million+ miles, started 2nd million on 8/24/13 Now past 1.3 million and going strong.

02-07-2018, 10:33 AM	#15
CorneliusRox Name: CorneliusRox Title: Seasoned Rookie Status: Not Here Join Date: Dec 2012 Location: Detroit, MI Member`s Gallery Posts: 4,154	That old PCM service manual is such crap though. It drives me crazy. __________________ Corey - BSME '21 Tesla Model 3 Perf '22 DMax AT4 2500

02-07-2018, 12:49 PM	#16
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	Thanks everyone! I pushed it to the side. Will prob get too it Friday. Will post my findings.

02-12-2018, 11:02 AM	#18
95cummins5.9 Name: 95cummins5.9 Title: Old man *** gossiper Status: Not Here Join Date: Jun 2012 Location: U.S.A Member`s Gallery Posts:** 4,720	Ok guys, the servo tested 84.4 ohms on all but one pin which had 42.4 ohm. Assuming that points to a bad servo.. I did end up jumping 12 volts to the yellow and red wire, and that does give me my light, but under no circumstances does it ever have power, running, key on not running etc , without the jumper power wire. With it jumped I do get power to the servo plug, it has good ground, continuity etc. The pcm test Gary put up rules out the pcm ,from what I can tell. Anything else beside swapping clock springs and or giving direct power? Im not following that it won't pulse the vacuum? Could you explain a little more? Thank for taking the time to help fellas.