Very detailed ECU relearn, according to ChatGPT (28 Viewers)

[kty]

I've been trying to solve sluggish acceleration in my higher mileage LC200 (sluggish compared to my other 200, which has a lot more pop) for awhile. I'd done fuel injector cleaning, induction maintenance, ECU reset, etc., without any improvement.

Last week I took it to a different trusted LC mechanic for another opinion. He said the plugs were gapped wrong and old, so we did that. Still not much of a difference.

Meanwhile I've got a thread going with ChatGPT about this (I use a project with my truck's maintenance history stored as knowledge). When I mentioned what the mechanic said about the plugs being gapped wrong, GPT suggested doing a very methodical and detailed ECU relearn.

So I'm curious -- is this just BS or is it worth the trouble of driving somewhere to properly attempt this? Here's what it suggested:

This driving routine helps accelerate adaptive learning, especially for:

• Throttle response
• Air/fuel ratio (short- and long-term fuel trims)
• Transmission shift logic
• Torque converter behavior

Prep Steps (Before Driving)​

1. Clear Adaptations (Optional but Ideal):
   • Disconnect negative battery terminal for 10+ minutes.
   • Press brake pedal while disconnected (discharges ECU capacitors).
   • Reconnect and start vehicle without touching the throttle.
   • Let it idle for 5–10 minutes, then shut off.
2. Confirm Proper Warm-Up:
   • Before starting the drive, make sure:
     • Engine coolant is up to temp (180–200°F)
     • Transmission fluid is warmed (at least 130°F)

Spirited ECU Relearn Driving Procedure​

Perform this on open, safe roads or highway stretches. Total time: ~20–30 min.

Phase 1: Low-Speed Precision (Throttle + Timing + Trim)​

Do this in a quiet residential or industrial area.

1. Drive at 20–25 mph
2. Use gentle throttle (5–15%) and hold steady
3. After 10–15 seconds, release throttle to coast
4. Repeat 6–8 times, gradually using more throttle (up to ~30%)

Purpose: Relearn closed-loop throttle and fuel trims

Phase 2: Medium-Speed Acceleration (Ignition + Load)​

Use a 40–55 mph road with a long straightaway.

1. From a stop or slow roll, accelerate to 50 mph at ~50–60% throttle
2. Let it hold a gear for 2–3 seconds before shifting
3. Coast or lightly brake to 20–25 mph
4. Repeat 4–5 times

Purpose: Teach ECU new timing/torque curve with higher cylinder pressure

Phase 3: Full-Load Pulls (Throttle + Shift Logic)​

Highway or open road only — do 3–4 wide open throttle pulls.

1. Roll from 20 mph → accelerate at WOT (100%) to 60–70 mph
2. Let off throttle and coast gently
3. Do it again with cruise control off
4. Bonus: Try one uphill if possible

Purpose: ECU calibrates peak load behavior (ignition, fueling, torque converter slip)

Phase 4: Cruise and Downshift​

1. Cruise at 60 mph for 3–5 minutes
2. Lightly tap throttle to force small downshifts
3. Let it coast again to idle
4. Pull over and let idle for 2 minutes

 

[04UZJ100]

Unplug battery. Reconnect battery. Drive.

That’s it.

 

[GrouchyTech]

Unplug battery. Reconnect battery. Drive.

That’s it.

That won't clear the transmission adaptation. However, I think there's another issue causing this problem.

 

[kty]

That won't clear the transmission adaptation. However, I think there's another issue causing this problem.

Me too honestly. What do you think it is?

Next up would be a compression test.

This truck has 250k. It still drives great, but my LC with 140k is noticeably quicker and more responsive esp at lower speeds.

 

[GrouchyTech]

Compression test, check fuel pressure/pump duty cycle should be good places to start.

Compared to your other 200–is it sluggish at all throttle positions? Do both your 200s have the same transmission (6 vs 8 speed)

 

[CanadianRockyCruiser]

Worth checking coils too! A failing coil doesn't always result in a CEL right away.

Fuel --> Spark --> Compression

 

[kty]

Compression test, check fuel pressure/pump duty cycle should be good places to start.

Compared to your other 200–is it sluggish at all throttle positions? Do both your 200s have the same transmission (6 vs 8 speed)

Thanks -- those are next up.

Both are 2015.

Sluggish in low to mid positions. Just feels like it's working harder and delivering less. I've a very steep hill on my street and the snappier truck practically flies up. The other climbs steadily but it ain't flyin'.

 

[kty]

Worth checking coils too! A failing coil doesn't always result in a CEL right away.

Fuel --> Spark --> Compression

Good call but supposedly the coils are fine according to the guy who just did the plugs.

 

[CanadianRockyCruiser]

Does the engine rev normally while in neutral? Can you confirm that this is not a transmission issue?

 

[rlynch356]

fuel filters also do this before they fail (i.e. clogged)..

 

[32cls6speedmt]

fuel filters also do this before they fail (i.e. clogged)..

Does 200 have fuel filter?

 

[GrouchyTech]

Does 200 have fuel filter?

In tank