GDE Tune & CELs

[yarmo]

Sorry for the long post. I’ve been chasing CELs on my JL ecodiesel for months now, and I’m looking for advice. I’ve got a tune from GDE, and it’s fantastic, I have only good things to say about them & the tune. Unfortunately, I’ve been recently getting a ton of codes from it, and I don’t get what’s making it happen. GDE currently has my tuned ECU (they’re testing it), but does anyone have any ideas?

I keep getting a CEL for an injector P0206 (cylinder 6). I’ve cleared it 7 or 8 times over a few weeks, but it keeps coming back. I pulled off the engine cover and checked connections, but I don’t see anything out of place. There are no performance hits I can feel, and nothing else seems to be wrong. I also get a few others simultaneously like a P1514-87 and U0213-00. Last week my dash lit up with 12 codes at once plus a service transmission message. I got:

- P002F-E9
- C3409-96
- B00AA-AA
- B0600-2B
- P1400-00
- U0000-00
- P0000-00
- P07E4-00
- U0100-00
- P0402-00
- P2227-00
- P0101-00

Since then I swapped back to my stock ECU (plus detuned the trans), and I haven’t gotten any codes since. I searched all around wiring harnesses under the hood to see if a wire had gotten chaffed somewhere, but I don’t see anything wrong. The stock ECU fixing everything makes me think something’s wrong with my tuned ECU.

The CELs tended to happen at lower speeds mostly when I was coming down from 45 mph to 5-10 when i’d pull into my driveway or stop at a light. That’s why I initially thought it was a wiring issue, but I’ve still had 0 faults with my stock ECU after hundreds of miles. It would also show up when I remote started it / at startup. The last time that threw 10+ codes was pulling into a parking space, it always seems to be low speeds, not when the engine is under load.

**I have a new battery within the last year, deleted the aux battery for start/stop, I checked the wiring harness next to the down pipe, and I have had the HPFP recall done**

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[Grayhound]

Was the tuned ecu new or used? How many miles with the tune?

 

[yarmo]

It was new in April 2023. I had their original tune for a few years, then last spring I had them remap it to their afterlife tune. I initially got a CEL or two for the DPF/EGR, but those eventually went away after a while. I’ve probably put 3k on it with the most recent tune.

 

[BDinTX]

I dropped your post into Google Gemini. It’s reply:


This is a textbook diagnostic scenario, and the owner provided enough clues to pretty much pinpoint the culprit. Since they’ve ruled out the usual suspects (new main battery, aux battery deleted, downpipe harness checked, and HPFP recall completed), you can give them a very clear breakdown:

Key Takeaway: It’s a Hardware Defect in the Tuned ECU
The absolute biggest clue in their post is: "Swapped back to my stock ECU... 0 faults after hundreds of miles."

If there were a physical harness chaff, damaged injector coil on Cylinder 6, or a bad sensor on the engine, the stock ECU would throw the exact same codes. Modern Bosch ECUs on the 3.0L EcoDiesel are extremely sensitive. The fact that the stock PCM runs flawlessly proves the Jeep’s actual vehicle wiring and engine sensors are 100% fine.

What’s Happening Under the Hood

1. Failing Injector Driver / Board Component (P0206): The recurring P0206 (Cylinder 6 Injector Circuit) with zero seat-of-the-pants misfires points to a cold-solder joint or failing internal MOSFET driver inside that specific tuned ECU casing. The ECU monitors circuit resistance milliseconds at a time; if the board driver momentarily drops reference voltage, it trips the DTC without a noticeable engine stumble.
2. Deceleration & Low-Speed Voltage Drop / CAN Bus Crash: The owner noted codes popping up at low speeds, decel (45 → 5 mph), remote start, or parking spots. On modern JLs:
   • When decelerating or idling, engine RPM drops, alternator output dips slightly, and system voltage fluctuates.
   • When Coasting/Decelerating, the ECU commands zero fuel cut-off (DFCO) and adjusts throttle/EGR states.
   • If an internal power rail or driver on the tuned ECU circuit board is failing, those micro voltage fluctuations or high-demand ECU state changes cause the internal board voltage to sag. This trips a cascade of false sensor faults (P0402, P0101, P2227) and causes a temporary CAN bus timeout (U0100, U0000, U0213), which triggers the "Christmas Tree" dash and service transmission message.
3. Bent Pin or Poor Connector Contact: During bench flashing or cloning, ECU header pins can get subtly bent, spread, or tarnished. An intermittent pin contact on the main ECU plug will cause random loss-of-communication codes (U codes) when the body vibrates lightly at low RPM/idle.

What You Can Reply / Suggest to Them
Here is a great response you can post or pass along:

You’ve already done the ultimate test by running the stock ECU for hundreds of miles error-free.
Because the stock ECU runs clean, you can completely eliminate physical engine harness chafing, a bad Cylinder 6 injector, or sensor issues. The problem is isolated entirely to the physical hardware of your tuned ECU.
A few likely culprits for GDE to check on their bench:

1. Internal Injector Driver Failure: The P0206 on an engine that runs smoothly usually means the MOSFET driver for Cylinder 6 inside the ECU casing is failing or has a bad solder joint, sending false resistance values to the processor.
2. Voltage Regulator / Power Rail Fault: Low-speed deceleration and idling lower alternator output slightly. If an internal voltage regulator or capacitor on the tuned ECU's board is breaking down, that slight voltage sag triggers a micro-second CAN-bus shutdown (U0100/U0000) and throws 10+ phantom sensor codes at once.
3. Pin Fitment: Check the physical pins on the tuned ECU headers to ensure none are slightly pushed back or spread from bench flashing.

Recommendation: Let GDE know that the stock ECU runs 100% code-free. They will likely need to clone your tune onto a fresh ECU board (replacement PCM) rather than just re-flashing your current hardware.

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