CarrHarris

I have an 03 S8 with 190k on it. It will crank but not fire, last time it ran, it fired ran for 2-3 sec then died, after that it would crank and not fire. I pulled the instrument cluster and re-connected it. Ross Tech'ed and got code P0668 whch does seem to relate to the issue, the battery is going weak from continued cranking. I am guessing the Crank Position Sensor. Any thoughts? TIA

jmmillerfzr

I think you are on the right track. Crank position sensor will not always throw a code. At 190k I would also look at fuel pump if it has never been replaced. If replacing the cps buy the bosch, I went down the cheap path and wasted a week. CPS is pretty cheap and easy to do, I ordered mine from FCP and they priced matched, $75 and less than an hour to replace. The fuel pump is a job, did mine in three hours, but not one of my favorite afternoons. Also make sure your battery is charged, I've noticed this car seems sensitive to low voltage.

silverd2

I fail to see what is steering you toward the engine speed sensor ("crank position") "G28" ??

G28 has nothing to do with internal temps or voltage supply. It will trip its own failure codes, like P0321 or P0322.

Generally, if engine is stalling and there's no code to go with it, it's more likely to be a failing fuel pump, which throws no code of its own.

CarrHarris

Will test the fuel pump before replacing the crank sensor, but the car did not falter, stall or stop running once started except for the last start for approx 2-3 seconds.

jmmillerfzr

That sounds more fuel pump. I found when I pulled my pump I could get it to work on the bench most of the time. It would get stuck every so often. I had about a month of harder starts before it gave up and left me stuck at work.

silverd2

That is an excellent description of the engine speed sensor NOT being the problem. If defective, it is much more likely to fail once warmed up.

Have you watched the immobilizer icon (key in the outline of a car) in the instrument cluster, to make certain it goes off when attempting to start the engine?

CarrHarris

The key symbol goes off when the car is started not while cranking. What does this mean?!?

silverd2

If the immobilizer lost contact with the key "chip", then the car could start, but shut off after about 2 seconds ... and the icon would stay on ... it goes out when recognized.

Normally, the icon should go out in a few seconds just with the ignition switch on ... not started or running.

twentysevenlitres

The immobiliser icon will also flash when not recognised or key lost contact both before and after start/stall and ignition on.

CarrHarris

My immobilser is working fine, my fuel pump makes some noise only noticeable if I have the trunk open not able to hear it from the cabin.