Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2009 dodge challenger rt with 5.7 engine no crank, no start and no communication
I've got a issue with a dodge challenger not starting. Get a etc error, cel and no crank condition. Can't connect with the pcm. The dlc power and grounds check out okay and the can connectors have 2.5v and 60ohm across. Found that the mds harness had insulation melted on all wires. Repaired the connector and replaced the MDS jumper harness. Also found the 5v the ect is on had 3vs. Replaced the oil pressure sensor and it went back to 5v. Also fixed the wires for 2 injection modules. Also tried a replacement pcm that was programed and throttle control module. There's a parasitic draw of .185amps and the problem of not cranking isn't resolved yet. Can't find whats causing the parasitc draw even after unpluging the tipm, alternator and power distrubution block in the trunk. Also found that a rodent has been in the engine bay, cabin and trunk.
Defiantly not good to assume. I checked the powers and grounds on the pcm as well as the can bus. Only found the one that was 3v. Thought I was on the right path since it shares the cranksensor, oil pressure sensor, maf sensor and etc sensors. That made me think it might be the pcm got fried and bought a rebuilt one. Not sure if the rebuilt one is bad since the symptoms are the same.
No codes at all, tried a few scanners that worked before but they can't connect at all. I've been digging around in the dash looking for damaged wire but haven't found anything.
If the DLC has good power and grounds and you have 60 ohms, 2.5 v on both can lines at the DLC and 60 ohms, 2,5v on the can lines at the PCM connectors as well as good powers and grounds at the pcm, you should be able to communicate to it.
Keeps pointing to a bad pcm. I've emailed the rebuilder about getting another one. Also they sent one that had a slightly different part number. I wonder if an older pcm doesn't support vvt on the 2009 5.7 engine.
I'm pulling about the dash and wonder if there's a chewed wire somewhere or the cluster is causing the problem with not being able to communicate with anything with the dtc.
Have you hooked a scope to your can lines at the dlc? I’d bet you have a module somewhere on the network that it talking a bunch of nonsense and causing the network to go dead. You can think of it like the one really drunk guy at a party yelling a bunch of random nonsense and no one else in the room can talk over him. If you scope the network and find that you have a good square wave pattern from 2.5v to 3.5 or 2.5 to 1.5 on can high and can low, then you can for sure decide that this is not your issue. I believe however that you have a module that is staying awake all the time and talking a bunch of nonsense on the network. This can be caused by bad powers or grounds to the module in question so be careful you do all your checks before condemning a module
Good point, thanks for explaing what a good wave pattern should look like. I just ordered a scope. Well a DMM with a scope function. In the meantime, I'd start checking the modules that share the can c bus. There is also an airbag light, so maybe start there.
Found that the IAT sensor that is pugged on the sensor ground that is shared with the crankcase sensor and oil pressure sensor is pulling that circuit to 4v. It's 4.9 without it plugged in or across the pins in the connector. Ordered a new oem sensor to replace it.
Been checking the modules that share the can c bus. If I measure at the dlc, I get 2.5v across the can+ and can- wires as well as each can wire with the body ground. When measuring at the shift sensor I only 2.5v when measuring the can+ or can- with the ground. I get about 300mv when measuring across the can- and can+ wires. Not sure if that's normal.
IAT is a thermistor, it does not pull the 5v ref to ground as potentiometers do.
When you get your graphing multimeter, you can scope the can lines at any module and post the result. The graph would help others to help you better.
Assuming is never a good thing.
Last edit: 7 months 3 days ago by Monde.
The following user(s) said Thank You: ChallengerDude
If I measure at the dlc, I get 2.5v across the can+ and can- wires as well as each can wire with the body ground. When measuring at the shift sensor I only 2.5v when measuring the can+ or can- with the ground. I get about 300mv when measuring across the can- and can+ wires. Not sure if that's normal.
All measurement of termination resistance is done with the vehicle battery disconnected.
The dominant nodes on the CAN-C bus are the WIN and the Powertrain Control Module (PCM). The termination resistance of the two dominant nodes are combined in parallel to provide a total of about 60 Ohms.
Total resistance of the CAN-C network can also be measured (60 Ohms)
If there are intermittent or active faults in the CAN network, a diagnostic scan tool connected to the Diagnostic CAN-C bus through the 16-way Data Link Connector (DLC) may only be able to communicate with the TIPM. To aid in CAN network diagnosis, the TIPM provides CAN-B and CAN-C network status information to the scan tool using certain diagnostic signals.
Last edit: 7 months 3 days ago by ferris48.
The following user(s) said Thank You: ChallengerDude
So what would cause that circuit to go down to 4v when the iat is plugged in? is there a short somewhere that it's taking over sending the voltage through the iat? Or is that normal?
The wiring diagram shows the diagnostic can c bus going to the TIPM and the can c coming out of it. I think I might try to hook up the scope to can c after the tipm as well. Could the tipm produce bad voltage on can c that's keeping the pcm from communicating?
So what would cause that circuit to go down to 4v when the iat is plugged in? is there a short somewhere that it's taking over sending the voltage through the iat? Or is that normal?
totally normal.
The temp sensor circuit has a current limiting resistor inside the computer so it's perfectly fine to pull that 5v signal straight to ground without affecting the other sensor using the 5v reference circuit. That's why when you're checking for shorted sensors it's useless to unplug temp sensors. But if you want to check for a 5v, you unplug it. If it goes to 5, the 5v ref circuit is probably fine.
Could the tipm produce bad voltage on can c that's keeping the pcm from communicating?
Anything is possible. If it comes to that point, you'd watch the signal waveform to return to normal after unplugging the tipm.
Your previous measurements at the DLC and at the shifter didn't read as too alarming but a waveform wouldn't hurt either
Here's what the can bus from the dlc looks like. Not sure what would cause that wave form.
I think you have this single channel scope hooked like this: can high on red lead and can low on black lead. This would explain the absence of the bias voltage. To check for proper bus bias, you'd want to hook up your scope to battery negative.
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