Cruise control problems

[Philip]

If your truck is having problems with cruise kicking off every once in a while on bumps. Check the wiring harness going into the PCM. The wires going into the PCM socket are very tight. This will stretch the terminal out and make a intermittent contact.



The solution is to take a very small screw driver and tighten the terminal back up by bending it back to a round shape agin. Be very carefull on this. Look at the sockets on the other end of the plug and try to make them the same size. If you tighten to much you could drive a pin threw the back side of the PCM and distory it when you reinstall the connection.



The terminal for the TPS wire is in the center row> second socket from the left side> looking into the PCM harness plug/connection.



If you loose cruise controll and not OD. Check the air gap on your RPM sensor. If it is off. It can drop your cruise and not OD. You might not loose your charging system on this one. I only lost charging one time in a 3 day period after a TPS change and the PCM socket fix.



P. B. if you think this should be in the FAQ section move it over.

 

[MFalkinham]

Another possible reason for losing cruise control during bumps might be bouncing of the brake pedal. I had to add a small return spring between the brake pedal bracket and the dashboard to take up the slop, which solved the problem for me. Another side effect of the W350 "ride quality".



- Mike

 

[Philip]

I know about the brake pedal problem. On my truck you have to launch the rear tires off the ground to get the brake pedal to bounce that much. I try not to turn the cruise off that way.



The things I listed were problems I found during my repairs. The bumps that were turning off the cruise were expansion joints on a 4 lane highway that was smooth. I did one troubleshooting fix at a time till the problem was gone.



The funny part was the droping cruise on bumps never happened with the old TPS. I installed the new one and set the voltage properly. Then the droped cruise problem jumps up. LOL



The RPM sensor happened a couple of days later during a heavy rain. I hooked the tach up for troubleshooting and it was showing a steady cruise RPM of 3k at 55 MPH. With my 3:07 gears I dought that. Some how the gap had closed up. I opened it up to about 1/8" and the cruise came back. I had OD all the time on the RPM sensor malfunction. Just no cruise.

 

[Philip]

I thought I would bring this one back to the top for a update.



I lost OD and cruise control agin today. My tach needle was jumping around and doing all sorts of funny things. When I got back home I checked the air gap agin. It was right where I had set in a month ago. The problem this time was the plug from the main harness to the RPM sensor. The terminals were egg shaped on this connection. The repair is not the same as the PCM repair. This connection has small tabs which make contact with the pins in the Sensor plug. Bend these small tabs back out to make contact. You have to look close to see them. They blend in good inside the female connection.



Now for the news I found out at the dealer. I stoped and checked to see if they had a sensor in stock. Just in case I needed one. This sensor is the same between a gasser and our trucks. Dodge only showed one in the books for both 5. 9's. The dealer had one in stock so I looked at it. It was the same.

Dealer cost was around $130, NAPA cost was $46. NAPA did not list it for our trucks with auto. But they did on a manual trans the gasser and diesel show as the same number. Dodge showed the same sensor for both auto and manual trans.



I checked mine out by the gasser section steps and it tested the same. Our FSM are not showing the plugs as what the trucks do have. The manual shows it as a flat 3 pin connector. Ours is a three pin triangle configuration. So you have to play around with a volt meter a little bit to find your power and ground wires. The other is your signal wire.