Trace a check-engine code and a tank that won't fill to a stuck valve with Grok, and fix it for $120

Posted

Aug 29, 2026 by Christopher Wipper (X)

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Last checked

Oct 19, 2026

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Method:

How we verify

Evidence: Screenshots or logsThe source shows screenshots, a transcript or the agent's output.

Outcome

Christopher Wipper's mechanic wanted $169 just to troubleshoot a check engine light. AutoZone's free OBD2 scanner gave code P0458 (purge control valve circuit low), and the car wouldn't take fuel: it backed up in the fill tube. With no YouTube videos for the problem, Wipper used Grok to troubleshoot step by step: the air drain case on top of the fill port was clear, but the canister close valve's solenoid was stuck closed. Wipper had the replacement part in hand in 20 minutes and fixed it for $120 in less than an hour.

Agent

Grok

The source didn't share its exact prompt, so we wrote this from what it describes.

Run this task now, exactly as written below. Everything you need is here, so start straight away and only stop if something required is missing or a rule below tells you to.

Goal: Help me work out what's causing this fault code and symptom, starting with the cheapest and easiest checks.

Fill in before running:
- Car (year, make, model, engine): [DETAILS]
- Fault code(s) from the scanner: [CODES]
- Symptoms and when they happen: [DETAILS]

Safety first: anything touching brakes, steering, airbags, fuel lines or lifting the car is a job for a qualified mechanic unless I confirm I have the tools and experience. Say so clearly.

Rules:
- Explain what the code means in plain words.
- List the likely causes from most to least likely, with a quick check for each.
- Walk me through one check at a time and wait for what I find before moving on.
- Tell me which part to buy only once a check points to it, and roughly what it costs.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.

Output: A step-by-step check list and, once found, the likely faulty part.

You'll know it worked when: I find the faulty part and the light stays off after the fix.

Run this task now, exactly as written below. Everything you need is here, so start straight away and only stop if something required is missing or a rule below tells you to.

Goal: Help me work out what's causing this fault code and symptom, starting with the cheapest and easiest checks.

Fill in before running:
- Car (year, make, model, engine): [DETAILS]
- Fault code(s) from the scanner: [CODES]
- Symptoms and when they happen: [DETAILS]

Safety first: anything touching brakes, steering, airbags, fuel lines or lifting the car is a job for a qualified mechanic unless I confirm I have the tools and experience. Say so clearly.

Rules:
- Explain what the code means in plain words.
- List the likely causes from most to least likely, with a quick check for each.
- Walk me through one check at a time and wait for what I find before moving on.
- Tell me which part to buy only once a check points to it, and roughly what it costs.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.

Output: A step-by-step check list and, once found, the likely faulty part.

You'll know it worked when: I find the faulty part and the light stays off after the fix.

Run this task now, exactly as written below. Everything you need is here, so start straight away and only stop if something required is missing or a rule below tells you to.

Goal: Help me work out what's causing this fault code and symptom, starting with the cheapest and easiest checks.

Fill in before running:
- Car (year, make, model, engine): [DETAILS]
- Fault code(s) from the scanner: [CODES]
- Symptoms and when they happen: [DETAILS]

Safety first: anything touching brakes, steering, airbags, fuel lines or lifting the car is a job for a qualified mechanic unless I confirm I have the tools and experience. Say so clearly.

Rules:
- Explain what the code means in plain words.
- List the likely causes from most to least likely, with a quick check for each.
- Walk me through one check at a time and wait for what I find before moving on.
- Tell me which part to buy only once a check points to it, and roughly what it costs.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.
- Tell me how to confirm the fix (clearing the code and what to watch for).

Output: A step-by-step check list and, once found, the likely faulty part.

You'll know it worked when: I find the faulty part and the light stays off after the fix.

Before you finish: re-read my goal and constraints, check your answer against each one, and list anything you assumed or couldn't confirm.

Source

https://x.com/SGTWipper1Each/status/2093820992091005386