Folks, I've tried getting feedback on the town and country forum but not much response. Gonna hope for better luck here. I have a 2014 Town and country 3.6 vvt that has been giving me fits. a few weeks ago it went into limp mode while I was on the freeway. ugh. I'm a fair diy guy and have been doing all I can to figure this out. yes I'v thrown some parts at it but still I've only spent about $600 and I figure that's still cheaper than a few hours with a mechanic or dealer so I'm not quite ready to quit on it. The van runs great, engine sounds great. No foul exhaust odors or smoke. Lightning bolt I know is related to throttle body or pedal. But question...if car goes into limp, will lightning bolt always come on regardless of cause? I am getting consistent 0420 (catalytic below threshold) and 0642 (powertrain control module failure) with cel after a handful of drive cycles after clearing codes. In order of replacement, I did 1. battery $200 2. alternator $150 3. throttle body $60 4. accelerator pedal ($54 ebay salvage) 5. bank one o2 sensors $150 oem.
After every item, it's same result......drives great, sounds great, smells great, then boom, p0420 pops up followed shortly by 0642 and limp with lightning bolt.

One thing has not changed....my accelerator pedal sensor E bounces between 4.35 or so to 0. Pedal sensor D remains steady at 8.32 .....both change with acceleration. My other cars have stable pedal sensor voltage. I'm left thinking next thing I want to change is the ecu which can be had as a reflashed and programmed to the vin for $175. The other thing is the bank one catalytic itself but I'm really trying to avoid that.

The engine is not clean. It has a small oil leak which has coated a lot of the top surface area of the transmission top. Can anyone tell me if the fluctuating pedal E sensor voltage cause the ecu to throw the car into limp? Is there a required reprogramming after throttle body and or pedal assembly? If so, and I did not reprogram, is it possible for the ecu to still be seeing old data from before parts were replaced?

I'm hoping for diy help still, not take it to the dealer. Thank you all

 

p0642 is 5v sensor reference circuit low. Meaning the sensors on that circuit are not getting the full 5volts they need. SO wire issue PCM or one of the sensor is pulling down the 5v

 

thank you for the feedback.....I would like to find a wiring diagram for the 2014 3.6 vvt. can you steer me to a download of that? I will do another dive into external wiring inspection today. I would like to know which 5v sensors are possible culprits. The one symptom that keeps puzzling me is the accelerator pedal sensor E erratic behavior. That one on my OBD scanner is showing fluctuations to 0 for milliseconds and back to 4.25 constantly. Could it be that with the computer seeing 0 volts at that sensor repeatedly a number of times, sees the short and puts the van in limp? And this is a replacement pedal which is displaying the exact same erratic voltage on pedal sensor E as the original, so I don't think the short is at the pedal harness.
Is it also possible that the ecu itself is failing to send or see correct voltage from these sensors. Is the red lightning bolt SPECIFIC to throttle at the throttle body or pedal, or...will the red lightning bolt appear anytime the vehicle goes into limp?
You are always a good responder and know your stuff. I live in a small town with a handful of auto repair shops, but I am really skeptical that they have the expertise to diagnose an electrical glitch like this and would only be guessing, much like me. Thanks for you help.

 

the wire diagram will show what sensors are on that specific circuit. I dont have any place to download any service manuals sorry . The lighting bolt yes is to alert you there is an issue with the throttle control system and will put it in limp mode.

 

Thank you again for help. Update, this morning after inspecting wires and harnesses again, I indeed found a harness chafed thru and 2 small internal wires in a bundle of at least 20 that were chafed thru and laying on top of each other showing bare copper. It was the bundle going to transmission plug. Aha! I said.....I carefully separated and cleaned off the wires and insulated with electrical tape and made sure not laying against a contact point. I was really hoping this was it but after a test drive of no more than 5 miles, it went into limp again with the lighting bolt. The only codes that are appearing with this condition are the green "historical 0420" catalytic below threshold, and the 0642 "powertrain" showing up as pending. I'm depressed.
Question...when I replaced the throttle body, is there a super duper dealer service center throttle position relearn that must be performed?
or....could the ECU(PCM) just be the problem.? I have ordered a reflashed ECU still enroute, but I wasn't going to change it out if the frayed wires had solved the problem.

 

yes the throttle or pedal sensors need to be relearned after replacement

 

again, thanks for your help, but does the relearn require doing it with a pro scan tool? I've only been doing the pedal depress with key on multiple times.

 

yes needs a scan tool