I have a 2000 Jeep Grand Cherokee (WJ) and while it’s given me relatively few problems over it’s 20 year lifespan (<180K miles), recently it developed a problem where after about 15-30 minutes of driving, it would stall when coming to a stop, all the gauges would go dark, and then it would not start when cranked. If you left it for 15-30 minutes it would start again, but would stall again after some time.
Annoyingly, no DTC codes were logged, which made it difficult for my mechanic to diagnose, and their test drives failed to trigger the problem. I think if I’d had a scan tool available when the stalling occurred, the problem would have thrown a code.
In the end, it turned out to be a failing auto shut down (ASD) relay. I believe that its failure mode was to stop working when it gets hot, causing the engine to shut down.
My Jeep stalled again, this time while decelerating in a section of sluggish traffic on a freeway. I managed to have enough momentum to get her over to the shoulder, and as before, she started up after sitting for 15 minutes.
Took her to a different mechanic who replaced the fuel pump and fuel regulator. So far so good – one interesting thing is that previously I had seen an intermittent coolant low warning that would quickly flash on the overhead display, even though the coolant level was fine. That seems to have gone away after this fuel pump replacement.
I think we’ve reached a conclusion in this saga. The final fix in the end was to replace the ECU. My Jeep has not stalled in the 6 months since the fix.