J&P
Sverige / USA
J&P

Car problems

Page created as exemplification of using ChatGTP to try figure our problems in a car.

Executive Summary

  • I was kind of impressed by ChatGPTs rather good diagnoses AND descriptions of all warning indications.
  • Have scheduled service with nearest Lexus dealer for tomorrow (3.3 mi / 5.3 km away) Plan is limping over.
    • Did so, went well (getting over there i.e.) Diagnoses was a different matter…
  • (Did try OBD-II scanner but w/o any success trying to learn more.)
  • Problem was diagnosed to be ECM and comms related.

(ChatGPT) Q: What can be wrong…? …

What can be wrong…? The car starts but get all these light when start, and when put a gear into drive, the car jumps hard though still can be driven. Something feels very wrong.

(ChatGPT) A: I see the dashboard in your photo ….

I see the dashboard in your photo — multiple warning lights are on:
  • Check Engine (CEL)
  • ABS
  • Traction Control / VSC
  • AFS OFF (Adaptive Front Lighting System disabled)

Plus you described:

  • Car starts but jumps hard when shifting into drive
  • Still drives, but something feels very wrong

What this combination usually means

When several systems throw warnings together, it usually points to a shared issue affecting multiple control modules. Common causes:

  1. Engine / transmission issue
    • A failing sensor (e.g., MAF, crankshaft, throttle position, transmission speed sensors).
    • Transmission control problem — rough engagement into drive suggests it may be in “limp mode”.
  2. ABS / Traction disabled because of engine fault
    • If the engine computer detects a major fault, traction control and ABS can be disabled as a safety measure, which explains those lights.
  3. Electrical / power supply issue
    • Weak battery or bad alternator can trigger multiple warning lights at once and cause harsh shifting.

What you should do right away

  • Do not drive far until checked. Harsh shifting can cause serious transmission damage.
  • Check battery voltage (should be ~12.6V off, ~14V running). Low voltage = possible alternator or battery failure.
  • Read the codes with an OBD-II scanner — this will tell you the exact fault (engine, transmission, or ABS). Many auto parts stores scan for free.
  • If the car slams into gear, avoid driving it except directly to a mechanic.

⚠️ Since you’re seeing Check Engine + ABS + Traction Control + transmission harshness, this is likely a major drivability problem, not just a simple sensor glitch.

👉 Do you want me to walk you through how to quickly check the battery/alternator yourself before assuming it’s the transmission?

 

(Me) Do have an OBD-II Scanner …

… and try connecting and learning more on error codes, but it really doesn’t help me. Messy user interface and after maybe ten minutes of messing around screens, downloading data, still not getting any useful info out of it. Stop it and will drive car to Lexus dealer tomorrow. Did so, got diagnoses – next:

(By Lexus) Diagnoses – CAN comms problem

This can clearly explain my problems getting anything useful out of my own try to use OBD-II scanner above – with problems with car-local networking, it IS difficult to get anything out of the car. (CAN = Controller Area Network, a kind of specialized form of networking, in contrast to e.g. PAN (Personal Area ..), LAN (Local Area ..), WAN (Wide Area ..), et c.

Lexus: “TESTED FOR POWER AND GROUND TO THE ECT, AND TESTED THE CAN COMMUNICATIONS BETWEEN THE ECT AND ECM.
CONFIRMED THERE IS AN INTERNAL OPEN IN THE ECM CAUSING NO COMMUNICATION TO THE ECT. RECOMMEND REPLACING THE ECM.”

(ECM = Electronic Control Module, can also be Engine Control Module, ECU, Electronic/Engine Control Unit, … )