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Discussion Starter · #1 ·
SITUATION
2008 Jeep Grand Cherokee North Edition (Limited?) 3.0L CRD (MB OM642), 152,000 miles, GDE Eco Tune - "Delete" since bought used in 2015. At the end of a 2.5 hr drive (avg 75 MPH), hit a heavy downpour, at the end of which, the Electronic Throttle Control warning light (lightning bolt) began to flash and system went into Limp Mode. (You can drive 60 MPH on the flat, but it's a dog, and up a hill, you have to downshift). Briefly showed a battery/charging system fault. NO MIL (CEL). Autozone guy was surprised to get DTCs off the vehicle.

OTHER KNOWN ISSUES OF POSSIBLE RELEVANCE
Unresolved parasitic power loss. Battery takes charge to ~12.6 V. Alternator (replaced 2016) charges to ~14.8 V. Will lose charge in a week if not run or kept on a NOCO Genius (smart charger). When kept on a NOCO, it will charge off and on regardless. I performed a repair charge last week, then left in maintenance mode for several days last week prior to trip. Tested today with digital multimeter for parasitic power loss, but once the system went to sleep, it never seemed to register over 12 mA draw, but there seems to be some spiking I can't quantify.

ERROR CODES
P2100 (Throttle Actuator Control Range/Performance)
P0638 (Throttle Actuator Control Motor Circuit/Open)
P0672-5 (Glow Plugs 2-5)

ACTIONS TAKEN

1. Battery disconnected. No change on reconnect.
2. Tests for parasitic power loss. No constant loss over 50 mA (see above).
3. Tested glow plug resistance, which identified all but the plug in cylinder 6 are dead (resistance measuring in the KOhms range). Ordered Glow Plugs and controller as it has been identified as a potential cause of dead glow plugs, and with 5/6 dead, prudential judgement to replace the controller.
4. Accelerator pedal recalibration. No change.
5. Disconnected battery. Disconnected accelerator pedal and thottle actuator connectors. No change on ordered reconnection.

Next step I plan to take is to try to work the throttle mechanism, as what I've read sometimes the throttle flap just gets stuck.

Any ideas if my next step doesn't resolve it? Wanted to get this on the board because info on these things is somewhat limited due to low volume (2 years) and mine was a NAFTA used import from Canada.

Some guys have had to replace the turbo VVT actuator. Turbo is practically new (royal PITA to replace, and expensive as heck if you pay a mechanic), but the actuator isn't too difficult to access.
 

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I would concentrate on P0638 code first.
- check all the wiring around the throttlebody and the gas pedal.
- measure the resistance in the gas pedal.
The pedal seems to be a sometimes troublesome part due to the fact that it gets roadgrime and salt from the drivers shoes..
 
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Stuck throttle flaps are usually the swirlcontrol flaps, i tend to belive that the GDE tune keep these open all the time.
 
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I find no P2100 fault code listed for this vehicle in the factory service information.
The other part of the P0638 fault code is 'EGR Airflow Control Valve Performance'.
I would have suggested some more diagnosis before ordering a new ECM controller. The glow plug drivers can open, but they usually don't cause glow plug failure.
These diesels had a tendency to coke up EGR coolers, tubes and passages with carbon soot from poor fuel quality. Use only a good-quality ULSD fuel.
Mopar did offer some chemical cleaners for this issue:


 
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Discussion Starter · #5 ·
I find no P2100 fault code listed for this vehicle in the factory service information.
The other part of the P0638 fault code is 'EGR Airflow Control Valve Performance'.
I would have suggested some more diagnosis before ordering a new ECM controller. The glow plug drivers can open, but they usually don't cause glow plug failure.
Not the ECM controller, the Glow Plug Module 904-310. It's a small $150 box on Amazon, about $225 locally. BTW, everybody says there's no P2100 fault code, but it shows up on my machine and others have reported it. I have to wonder if Jeep and possibly Dodge didn't drop the ball when they wrote the books for these. Not sure what FL and MB systems report on these codes.

I'm pretty picky about fuel, especially for diesels.

These diesels had a tendency to coke up EGR coolers, tubes and passages with carbon soot from poor fuel quality. Use only a good-quality ULSD fuel.
EGR is disabled (GDE tune), so that shouldn't be an issue at this point. There's not even any oil residue coming through the system to coke it up, but there probably was plenty before I bought it in 2015. The turbo inlet was clean and dry (and there is oil in the EGR crossover into the air intake tube).

Anyway, thanks to all for the input. Makes sense to me.
 

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You said ..."limp mode" are you having any issues with the tranny? Limp mode means that your computer has stuck your tranny in a gear to help you get home due to a major issue.. sorta.
 

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I find no P2100 fault code listed for this vehicle in the factory service information.
The other part of the P0638 fault code is 'EGR Airflow Control Valve Performance'.
I would have suggested some more diagnosis before ordering a new ECM controller. The glow plug drivers can open, but they usually don't cause glow plug failure.
These diesels had a tendency to coke up EGR coolers, tubes and passages with carbon soot from poor fuel quality. Use only a good-quality ULSD fuel.
Mopar did offer some chemical cleaners for this issue:


Did not know that there is a EGR system cleaner... I'm going to look into that for my 6.4 Hemi 2500. Thanks
 

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Discussion Starter · #8 ·
You said ..."limp mode" are you having any issues with the tranny? Limp mode means that your computer has stuck your tranny in a gear to help you get home due to a major issue.. sorta.
Nothing really glaring that I'm aware of. More like the engine has reduced power. Not technically limp mode by that definition. It will shift to 3d with sufficient power (at least on flat ground) then it gets doggy in 4 and 5. I can manually downshift to get up hills, and am able to drive over 60 MPH on the flat no problem, just takes a bit to get up to speed. No MIL lamp, just the ETC lamp flashing. Ironically, I was planning on servicing the transmission soon, and had a TransGo shift kit and some Sonnax bits for a minor bit of shift lag and TCC damper updates. It has over 150k miles. That said, it wasn't giving me any real problems as far as I would know, as I never drove one new to know how it should drive. I was doing 75 MPH for 2 hours easy-peasy, hit a major rainstorm that brought us down to 35 MPH, got off the interstate 5 minutes later, then BOOM, ETC flashing and no power.
 
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Diesels will run on a 'de-rated torque' mode for engine mechanical protection with certain fault codes. It is a 'limp-in' mode.
 
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....something moisture related...

Had an Omni that did this in 1990. Took a huge rainstorm to get erratic engine operation. Could not duplicate it, even in a quarter car wash, soaking the engine compartment.

FINALLY - I took a hose and got some spray into the intake. BINGO. Engine started stumbling.
At that time the "computer" was in the intake horn. Traced it to potting material that would let moisture wick into the electronics.
New ECU and I was all set.

Just saying that the problem started in a huge rain storm, so I'd look into things that could get moisture into them...
Hope this insight helps.
 
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Discussion Starter · #11 ·
Update: Manually cycled the throttle flap a few times. This reset the Electronic Throttle Control alarm, but it came back when I started the vehicle. Note that I performed an APPS recalibration prior to starting. Seems to have something to do with the APPS and/or Throttle Controller, which is consistent with the DTCs.
 

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Update: Manually cycled the throttle flap a few times. This reset the Electronic Throttle Control alarm, but it came back when I started the vehicle. Note that I performed an APPS recalibration prior to starting. Seems to have something to do with the APPS and/or Throttle Controller, which is consistent with the DTCs.
How did you manually cycle the throttle plate?
 

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Discussion Starter · #13 ·
How did you manually cycle the throttle plate?
With a long 3/8 socket extension. There is a removable expansion chamber right above the throttle body that comes off easily allowing direct access to the throttle flap.
 

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Discussion Starter · #14 ·
Update No. 2: Second drive, ETC light still flashing, but the engine seems to be running more normally, will pull up hills without manual downshifting. Going to put new glow plugs and controller in this afternoon.
 

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Discussion Starter · #15 · (Edited)
Update No. 2: Second drive, ETC light still flashing, but the engine seems to be running slightly more normally, will pull up hills with less manual downshifting. Going to put new glow plugs and controller in this afternoon.
Glow plugs installed, but the Dorman GP controller had some QC issues, as the power plug would not properly seat.
 

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With a long 3/8 socket extension. There is a removable expansion chamber right above the throttle body that comes off easily allowing direct access to the throttle flap.
If you have electronic throttle control and turned the throttle plate manually, instead of with the motor, you have damaged it. Chrysler specifically warns against doing this.
 

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Discussion Starter · #17 ·
If you have electronic throttle control and turned the throttle plate manually, instead of with the motor, you have damaged it. Chrysler specifically warns against doing this.
That may be true on a gas throttle body, and perhaps you're right, but the MB throttle body plate doesn't perform the same function that a gas TB performs, FWIW. It moves freely and returns to open when pressure is removed. Doing so caused some degree of improvement in my engine's performance, or so it seems.
 

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Discussion Starter · #18 ·
The books call it an EGR Airflow Control Valve.
 

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If the GDE tune has disabled the EGR, that may be a problem if the sensors are still looking for EGR flow? Have you contacted GDE about the issue?
Diesels don't really have a throttle butterfly. Power output is controlled by fuel quantity (more like a furnace than a gasoline engine).
That butterfly is there to control pressure in the intake manifold for metering EGR flow.
Without EGR there is a possibility of excessive combustion (detonation) temperatures and pressures inside the cylinder that can do damage under load.
EGR isn't simply an add-on, power-robbing emissions device anymore. It is an integral part of the engine and fuel injection system.
 
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Discussion Starter · #20 ·
After replacing the ACCEL PEDAL ASSY, I now get some different codes. I'm processing an email to GDE regarding this, but electrical short in the Throttle/EGR flow control assy could be a problem, based on the P2141 EGR AIR FLOW THROTTLE CONTROL CIRCUIT A LOW code.

Here's the current situation after replacing the ACCEL PEDAL ASSY, clearing codes, and driving:
    • P2138 ACCELERATOR PEDAL POSITION SENSOR 1 / 2 CORRELATION
    • P2121 ACCELERATOR PEDAL POSITION SENSOR 1 PERFORMANCE
    • P2141 EGR AIR FLOW THROTTLE CONTROL CIRCUIT A LOW (ALLDATA DIY indicates possibly testing circuits for short)
    • P0488 EGR AIR FLOW THROTTLE CONTROL CIRCUIT PERFORMANCE -
    • U1132 (Generator comms – possibly related to the intermittent electrical system fault indicator lamp and intermittent parasitic power loss issue?)
  • Upon restart, ETC light stays off initially, and when cleared, no P2121/38 codes but ETC (and codes) resumes once pedal is actuated, leads me to believe I need a tech to recalibrate the TPS.
I've got a query in to Green Diesel now. I'm beginning to think perhaps part of the problem relates to this mystery intermittent parasitic power draw that keeps draining the battery, but I'm not knowledgeable on these things enough to know how. Dad talks about having a bad diode cause it on a 40 year old tractor, so it wouldn't surprise me on a 10 year old SUV.
 
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