Yet another "died while driving" thread. I have some troubleshooting to do but I was hoping for some suggestions ahead of time. I was driving yesterday, when I went home and parked for about 20 minutes. I went to start the Disco back up and the engine would crank nice and fast but would not start. I waited about 3 hours and tried again, and it started just fine.

Today, I drove about 20 minutes and it died on the roadway. There were no check engine codes and no symptoms prior to shutting off, not even sputtering or a loss of power- it just died out of nowhere. My coolant temperatures have been fine lately. Coincidence or not, I'm not sure, but I noticed my Ultraguage started reading "error" for the coolant temperature gauges, so I don't know what they were but the factory dummy gauge didn't rise above the normal halfway point. I've exerpienced overheating years ago, before headgaskets were replaced, and this did not mimic those symptoms. I do not believe it to be coolant related, at all.

Maybe a coincidence, maybe not, but my "S" and "M" lights started flashing a few days ago. I would turn the engine off and turn it back on and they were gone. It happened again yesterday, and, again, all I had to do was turn the engine off and turn it back on to resolve the problem. I've ensured the battery terminal connections are tight and the battery is only 9 months old. I know the flashing "S" and "M" are sometimes an indicator the XYZ switch has failed; it's something I'm researching at the moment.

The plan is to check for fuel and spark when I get a chance. Any thoughts or ideas for me to start with? I was thinking possibly the fuel pump. The Disco has about 140,000 miles on it.

 

Replying to myself....

I'm beginning to lean towards Crank Position Sensor. Similar posts have been made of the same shut off problem and the resolution was a new Crank Position Sensor.

 

Agreed. Classic symptoms of a failed crankshaft position sensor (CKPS). A failing CKPS will often work again after it cools down.

As I have recounted a few times before in this forum, the CKPS in my truck failed 12½ years ago mid-day Sunday when I had six boy scouts on board, headed home from a weekend ski trip. We were at a stop light, thankfully, when the engine simply died a hundred miles from home. No warning. Like turning off a light switch. I'm very thankful it didn't fail while the truck was moving, let alone if I had been on a highway at 65 mph. After a little bit the truck started again and we made it a bit farther before it died a second time, but in a safer location. I'd read enough on this forum by then to know what the problem was immediately.

I had to call a parent to have him come pick us up in his minivan, and I had the truck taken by a local towing company to its lot. I drove back the next day, replaced the CKPS, and all was well.

The worst part by far about replacing the CKPS is reaching the damnable connector behind the engine. Replacing the sensor itself is easy.

As for the flashing M&S lights, they indicate any of 14 transmission faults listed in the RAVE, only one of which is XYZ switch-related. The most common cause of the flashing M&S lights is low voltage. The transmission ECU is very finicky about voltage. Start by removing, cleaning and reinstalling the battery terminal clamps.

 

Yep, CKPS. I had one failing like this, it is temp related. Did not have time to swap it so I quickly fabbed an aluminum heat shield and shoved it in place. That was 4 years ago, haven't had any further problems. If you do change it wrap the factory cover in aluminum foil to prevent a recurrence.

 

Why not just wrap the one on his truck now and see if that does the job like it did for you?

 

Could definitely work...

 

I may add a shield for the CKPS in my truck as a preventive measure. Extinct, how about a pic next time you're under the truck?

 

I am sure you guys are right, however when mine went out it was not temp related. Over several days it did work intermittently, but leaving it over night did not reliably fix it. Seemed completely random. Sometimes would restart immediately other times it took a few attempts. Sitting overnight did not matter. All that to say is that if you have small hands its an easy job. It is helpful to plug in the connector before installing the sensor. In my experience. I do not have small hands. I would just replace it for reliability sakes.

 

Crankshaft position sensor successfully installed.

Two exhaust studs successfully sheared.

The sensor install was definitely a PITA, but only took about an hour and a half. I was not able to get my forearm past the exhaust pipe without unbolting it from the manifold. Even then, I had a very difficult time getting in close enough to manipulate the harness clips. After the sensor was unbolted, I had to fish it out from under the hood with a coat hanger- no matter what I tried, I could not unsnap the harness clip from under the vehicle. One thing that would have helped me save time and frustration is if I had known what type of harness clip I was dealing with, so here is a picture of it for anybody that needs to know:



I had to stick a pick under the tab the arrow is coming from and move the tab in the direction of the arrow, while pulling the plug out of the harness clip.


I haven't had a chance to go on a long enough test drive to know if I've solved my problem but it starts up and seems to be running fine. Now I have to find a way to remove the sheared exhaust studs from the manifold, but that's a problem for another day.

 

Thanks for keeping us updated.