Cruise control not working

Hi,

Just to clarify, when you turn the cruise on, does the dash light come on to show the system is on and it just doesn't set? Or when you press the on button does the dash light not even come on?

I attached the description of the system and the wiring diagram. As you can see from the diagram, the switch inputs are all a direct feed to the PCM. I assume you are saying the horn still works to rule out the clock-spring?

If the light doesn't come on at all, I suspect the PCM is not getting the input from pressing the button. Is there a chance that this has not been working for a while and not related to what you installed? How often do you use the cruise or do you remember the last time you used it?

If the light on the dash does come on, I suspect your brake switch may have failed and the PCM thinks the brakes are so it doesn't activate the system, however the light on the dash should still come on.

Last thing, is we need to see if there are any codes. If you have a circuit issue, I suspect you have some codes. Let me know if you have a scan tool that you can see live data as well as codes.

Thanks

Okay. What exactly did you install? You said lights that come off the battery but where did you run the wiring and where did you place the switches?

The fact that the light does not come on in the dash tells us that the PCM is not seeing you press the switch. That means it is either not getting the signal or the switch is not working.

You are correct. An auto parts store can pull any codes. Hopefully we have a circuit code or something to go on. Otherwise, we will be left with wiring testing with a meter.

Let me know and we can go from there. Thanks

Unfortunately, those are for engine codes and on even older vehicles, some cluster codes. We are looking for a circuit code which will be stored in the PCM. It is not a code that will turn the engine light on so we need to see if the PCM is seeing an open circuit.

If not, it could be a faulty switch. The best way to test that is with a scan tool and see if the PCM is seeing you press the button.

With no scan tool, you will need to hook a voltage meter to the PCM pins and press the button to see if the voltage is getting to the PCM. You will need to monitor the two wires coming from the SCCM.

This is not the easiest test so that is why I am hoping you have a code in the system.

Okay. The C116A is most likely your issue causing the traction control light to be on and the cruise to not work.

Has this light been on or did it just come on when the cruise stopped working?

They are correct about the P1000 code. This just means that some of the sensors have not learned in the PCM and usually happens when the battery is disconnected or the memory of a module (usually PCM) has been cleared by clearing codes.

Let's focus on the C116A. This code is telling you that the PCM thinks the brakes are depressed or at least there is an issue with the circuit. Furthermore, the ABS is comparing the pressure on the transducer to the signal it is receiving from the brake switch and they don't match. In other words, the most common cause of this is the brake switch says the brakes are on but the pressure transducer does not see the brakes being depressed.

The brake switch is the electrical component that tells the PCM that the pedal is being depressed. The Transducer is the mechanical component that increases pressure when you actually press the pedal. These need to agree or you will set this code.

Correct. Without testing the system it is a guess but that is the most likely cause. If you want to take a stab at it then that is what I would do first. If that is not it, then you will need to run through the tests because I would not want to guess at a hydraulic control unit if it is a wiring issue.

Nothing specific. Unplug it and remove it and then install the new one and plug it in. This is not necessary to remove the battery.

This is pretty simple. The manual doesn't even give specific steps on how to do it or I would send them. I believe you have to twist them to "unlock" the brake switch from the pedal assembly.

I assume that the scanner that they used is not able to communicate with the ABS. The fact that nothing is different tells me the code is probably still there. Unfortunately this means you will need to dig a little deeper in the test that I provided earlier.

This specific code is stating that the brake switch input and the pressure transducer are saying different things. Unless you have a wiring issue, the pressure transducer is probably registering pressure which is different then what the brake switch is saying.

Unfortunately, there isn't a specific harness that I can point you to other than the connection point from the brake switch and the ABS/HCU.

I don't know any other way to verify proper operation without a scan tool to look at the ABS and PCM brake input. Basically, here is what you are looking for. When you press the brake pedal, does the PCM see the brake being depressed (Brake switch) and does the ABS see the brake being depressed (Pressure transducer)? If both see the brake being depressed then you have a wiring issue on the CAN network. If one or the other do not see the brake being depressed or see show it being depressed when it is not, then that is your issue.

At this point, you have eliminated the brake switch. So that means it is either the HCU (pressure transducer) or the CAN network wiring. Neither of which you want to guess at.

Unfortunately, I think we are at the point of needing a scan tool to figure this one out or a wrong choice can be pretty costly.