2021 JLUR (manual, 3.6L ESS) Won't Start

[Jebiruph]

In a single battery system and older electronics - yes. Diagrams suggest several relays between 2 batteries and a computer that fires the relays in a way that seems non-trivial to reverse engineer and make guesses about while lacking a correct wiring diagram. Also - eTorque?

There's only one relay between the batteries and there's no aux battery with the eTorque system, so that's a different conversation. In this case, the instrument panel would have blanked out during the start attempt if the issue was low battery power.

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[demisx]

Looking at the Starting Charging System 3.6L ESS diagram I do not see the Clutch pedal position sensor (68333561AB) being part of it. The "Clutch Interlock Switch (68029261AA)" is there, but this sensor is not.

With this being said, is it safe to assume that the "Clutch pedal position sensor (68333561AB)" has no affect on the start-up process and should be excluded from the suspect list?

P.S. I've tried to understand what this sensor does, but I could not find any info online. I've started a separate thread hoping someone will shed some light on it. https://www.jlwranglerforums.com/forum/threads/clutch-pedal-position-sensor-68333561ab.66683/

 

[gm920]

Looking at the Starting Charging System 3.6L ESS diagram I do not see the Clutch pedal position sensor (68333561AB) being part of it. The "Clutch Interlock Switch (68029261AA)" is there, but this sensor is not.

With this being said, is it safe to assume that the "Clutch pedal position sensor (68333561AB)" has no affect on the start-up process and should be excluded from the suspect list?

P.S. I've tried to understand what this sensor does, but I could not find any info online. I've started a separate thread hoping someone will shed some light on it. https://www.jlwranglerforums.com/forum/threads/clutch-pedal-position-sensor-68333561ab.66683/

Look at the manual transmission w/d. I would say the clutch pedal position sensor is the most likely culprit. The position sensor is the input to the PCM, which if correct the PCM then closes the interlock switch.

 

[demisx]

Look at the manual transmission w/d. I would say the clutch pedal position sensor is the most likely culprit. The position sensor is the input to the PCM, which if correct the PCM then closes the interlock switch.

Got it. I'll keep it on the list then. As far as the clutch interlock switch goes, are you sure the PCM closes it? I see this magnetic switch attached to the side of the clutch master cylinder and based on my research, this switch closes when the clutch pedal is depressed. I may be wrong, but I believe the clutch pedal closes it, not the PCM.

 

[eck]

Got it. I'll keep it on the list then. As far as the clutch interlock switch goes, are you sure the PCM closes it? I see this magnetic switch attached to the side of the clutch master cylinder and based on my research, this switch closes when the clutch pedal is depressed. I may be wrong, but I believe the clutch pedal closes it, not the PCM.

Correct, the interlock is just a physical switch

 

[NBB]

Have you run the engine for a significant amount of time for the aux battery to charge, then verified the problem repeats? You might spend a lot of hours chasing your tail if not. A pro at this point will pull codes, reset and look for returned codes - then move into the data stream and actuate the clutch to verify the computer seeing correct information. Lacking detailed specs and a factory grade scan tool, I suggest you find a sharp needle and stab it into a few of those wires and actuate clutch with ignition ON - verify switching and variable voltage with your Fluke DMM - both near sensor and computer connectors per wiring diagram. In particular, note clutch signal passes through radio-freq hub module before reaching ecm - test on both sides. What NOT to do is unplug things thus disturbing the system and possibly the problem itself, or to start replacing sensors on a brand new vehicle. Consider significant possibility you’ve damaged the radio-freq hub module, or you’re having voltage and logic threshold problems due to weak battery. For real - you might also consider driving to dealer - now that you can - and claiming a warranty issue after carefully removing your wiring project - hope they didn’t read this thread.

 

[demisx]

Have you run the engine for a significant amount of time for the aux battery to charge, then verified the problem repeats? You might spend a lot of hours chasing your tail if not. A pro at this point will pull codes, reset and look for returned codes - then move into the data stream and actuate the clutch to verify the computer seeing correct information. Lacking detailed specs and a factory grade scan tool, I suggest you find a sharp needle and stab it into a few of those wires and actuate clutch with ignition ON - verify switching and variable voltage with your Fluke DMM - both near sensor and computer connectors per wiring diagram. In particular, note clutch signal passes through radio-freq hub module before reaching ecm - test on both sides. What NOT to do is unplug things thus disturbing the system and possibly the problem itself, or to start replacing sensors on a brand new vehicle. Consider significant possibility you’ve damaged the radio-freq hub module, or you’re having voltage and logic threshold problems due to weak battery. For real - you might also consider driving to dealer - now that you can - and claiming a warranty issue after carefully removing your wiring project - hope they didn’t read this thread.

Thank you. No, I haven’t tried running it for an extended period of time, but I am running it now. How long do you suggest I leave it running for? I did have it on a trickle charge two nights in a row and so far haven’t seen any signs of a bad battery. I’m not saying it’s not and you may be absolutely right, but everything is pointing out to the clutch pedal position sensor so far. The battery is 2.5 months old with 2k miles of light street driving on it.

My dealership appointment is this Thursday. The OBD2 code reader should arrive tomorrow if there are no additional shipping delays. I’ll keep you all updated.

 

[NBB]

Close everything up, couple trips around the 'hood, shift to 2H, shut down and attempt re-start. After that, find a needle and located the wires you need to probe as in that wiring diagram - assuming it's valid for your vehicle, which it may not be. No success there means clean up all traces of your activities and bring to dealer. IMO.

EDIT - also, that OBD tool you've ordered may or may not see any of this. Never-the-less - is there an auto parts store nearby you can get to safely in 4L? Almost all have loaner OBD code readers. Reset while you are at it - if they let you as they are generally not allowed - but if so, reset and see if anything returns.

 

[demisx]

OK. I am wondering if I can rule out the battery issue now. Here is what I've tried:

1. Had the Jeep idling for 10 mins, then drove around the hood. No difference.
2. Tried to jump start it from a running Mercedes GLE 350 SUV. No difference.
3. Load tested both batteries per Jebiruph's post with the detail results posted here. Both batteries have passed the 100-amp load test @ 2 seconds.

Per @NBB's suggestion, I am going to use needles and test the clutch pedal position sensor next. There are three pings from it - 5V supply, sensor ground, and clutch position signal. Does anyone have any suggestions on how to test it beyond checking 5V supply? In order words, what should I see when I press the clutch pedal? Thank you.

Edit: I don’t feel comfortable driving to an auto store yet. I’m gonna wait for my OBD2 MX+ reader first and then go from there. It’s one of the expensive ones, so hopefully I get what I paid for. Planning on using it with JScan.

 

[eck]

OK. I am wondering if I can rule out the battery issue now. Here is what I've tried:

1. Had the Jeep idling for 10 mins, then drove around the hood. No difference.
2. Tried to jump start it from a running Mercedes GLE 350 SUV. No difference.
3. Load tested both batteries per Jebiruph's post with the detail results posted here. Both batteries have passed the 100-amp load test @ 2 seconds.

Per @NBB's suggestion, I am going to use needles and test the clutch pedal position sensor next. There are three pings from it - 5V supply, sensor ground, and clutch position signal. Does anyone have any suggestions on how to test it beyond checking 5V supply? In order words, what should I see when I press the clutch pedal? Thank you.

It's a potentiometer from the symbol in the wiring diagram. So you'll get something between 0V-5V on the yellow wire. You should see it change as you push the clutch pedal.

 

[NBB]

I would go for something indicated as “interlock” first, but if you insist - according to diagram - pin 3 = 5v, pin 2 = 0v and also 0ohms to ground, pin 4 voltage should vary somewhere between 0 and 5v as you press clutch. Problem is you have no spec to compare, but at least confirm what you can and note measurements.

 

[demisx]

Do you guy know how to get to that clutch pedal position sensor? Looks like there’s no access to it from outside.

 

[NBB]

Lol - that looks full-on. This is where the factory scan tool comes in so you don't have to go mining through sensors and wire bundles. It's not uncommon you can't reach a sensor, so you need to probe the wire at the ECU connector - which on a better designed vehicle should be reasonably accessible. Problem is you generally need to unwrap a large bundle of wires and the dealer will quite possibly go for the same bundle and notice someone has been in there. Really, I'd skip it, go after the clutch interlock switch, not position sensor, it's more likely the problem.

 

[demisx]

Lol - that looks full-on. This is where the factory scan tool comes in so you don't have to go mining through sensors and wire bundles. It's not uncommon you can't reach a sensor, so you need to probe the wire at the ECU connector - which on a better designed vehicle should be reasonably accessible. Problem is you generally need to unwrap a large bundle of wires and the dealer will quite possibly go for the same bundle and notice someone has been in there. Really, I'd skip it, go after the clutch interlock switch, not position sensor, it's more likely the problem.

Yeah, I’m gonna leave it as is. I enjoy learning my Jeep internals, but to a certain point. I am gonna wait for my OBD2 scanner tool and try to read codes next. Thank for holding me back from doing something stupid. Appreciate it.

As far as the clutch interlock switch goes, I’ve already confirmed this earlier that it’s working properly.

 

[NBB]

How did you confirm the switch was good? It pulls a signal to ground, so did you check both voltage on one wire and impedance to ground on the other - while pressing in clutch?

Note from diagram signal to this switch goes through radio freq module before ECU. Thus, if switch is confirmed good, then I think you need to find that RF module and probe both sides of it and/or where signal enters the ECU. Quick and dirty - disconnect related connectors and re-seat. Most electrical system issues are at the connectors.

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