Jeep Grand Cherokee: Crankshaft position sensor heat-soak — will not restart until it cools

The crankshaft position sensor on the petrol Grand Cherokees of this era is a classic heat-soak failure: it works perfectly cold, but once the engine bay is hot its internal resistance rises, the engine management loses the crank signal, and the engine either cuts out or refuses to restart. The pattern is unmistakable once you know it — the car starts and drives fine in the morning, then after a long run or a shopping stop it cranks over strongly and simply will not fire, and half an hour later it starts as if nothing happened. It is a cheap part, but a buyer who tests the car cold will never see it, and an owner who has learned to live with it has no reason to mention it. It also strands you, which on a family car matters more than the repair cost.

• Engine cuts out without warning while driving, then restarts later
• Cranks strongly but will not fire when hot, starts fine when cold
• Stalling at idle or when coming to a stop after a long run
• Intermittent engine warning light
• Hesitation or a stumble under acceleration when fully warm

The test is the drive itself, and it needs to be long enough. Drive the car for at least twenty to thirty minutes so the engine bay is thoroughly hot — a five-minute run around the block proves nothing here. Then switch it off, leave it sitting for five to ten minutes as you would at a shop, and start it again. A healthy car fires instantly; a failing sensor gives you strong, healthy cranking and no firing at all. Repeat the stop-and-restart once more if you can. While driving, note any momentary cut or stumble, and watch the dash for a warning light that appears and clears. Ask the seller straight out whether it has ever cut out or failed to start when hot, and whether the crank sensor has been replaced — many have, and a receipt for one is reassuring rather than alarming. If a workshop inspection is possible: have the stored codes read for crankshaft-signal faults, which log even when the car is running normally at the time.

$150 to $550 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has it ever cut out while driving, or refused to start when hot?”
• “Has the crankshaft position sensor ever been replaced?”
• “Does it ever stall when you come to a stop after a long drive?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.