Crank position failure?

Full-Timers · 10-28-2009, 10:09 PM

Looks like I got a bad crankshaft position sensor. On a trip today the motorhome shut down for a split second then again for a second then again for 2 seconds. Each time the tach dropped then, since I was moving, it restarted on its own and I kept on going. Then it died several times while idling during setup. Fortunately I have a mechanic friend that brought his code scanner over and, even though there were no CES light, found 2 codes. One was the CPS and the other was a communication failure between the tach and the PCM. Now I am thinking the tach code was because the tach dropped out during travel when the CPS failed.
What do you think?

Full-Timers · 10-28-2009, 10:29 PM

OK I just did some research and the tach thing is actually code P-1518 which is the TAC (Throttle Actuator Control) module. Now I am wondering if that might be my problem…TAC or CPS or both?

DriVer · 10-29-2009, 06:06 AM

Quote:

Originally Posted by Full-Timers

OK I just did some research and the tach thing is actually code P-1518 which is the TAC (Throttle Actuator Control) module. Now I am wondering if that might be my problem…TAC or CPS or both?

Full Timers, I don't want you to commit to buying a part on my say so however your failure certainly sounds consistent with a failed TAC. Call Brazels and ask to talk to Jon. He might just be able to give you a little better feel for what you're experiencing.

Hammerdown · 10-30-2009, 08:32 AM

Full Timers,

I just replaced my crankshaft sensor. Mine did stall a few times as well but the biggest problem I had was cranking without starting, as many as 20 tries in a row before I would let it rest.

Dick

DriVer · 10-30-2009, 08:48 AM

Quote:

Originally Posted by Hammerdown

I just replaced my crankshaft sensor. Mine did stall a few times as well but the biggest problem I had was cranking without starting, as many as 20 tries in a row before I would let it rest.

Dick, I had that very same event happen to me last year in a rest stop somewhere in Illinois. It eventually cleared and has not presented a problem since then. Preceding our little difficulty, our coach was struck by lightning and we sustained a few fried components including our TCM. You need to try driving hundreds of miles manually.

Photog · 10-30-2009, 09:23 AM

I had an ongoing problem with shutdowns and the TAC error code.

Replaced the TAC and so far no more shutwowns.

ARROWVP38 · 10-31-2009, 03:23 PM

Quote:

Originally Posted by Full-Timers

OK I just did some research and the tach thing is actually code P-1518 which is the TAC (Throttle Actuator Control) module. Now I am wondering if that might be my problem…TAC or CPS or both?

Just for my 2 cents worth is the motor a vortex if so I have had my chevy vans '03 '04'06 units with cps problems. It is common, they sit behind the starter ,I have had to retrive my vans because they just quit or they won't start .

Full-Timers · 11-03-2009, 10:35 PM

Well I took the motorhome to the shop today. They hooked the code reader again and found the same codes as last time, TAC to PCM communication error and Crankshaft Position Sensor out of range. But this time they also found a #8 plug wire misfire. They started by replacing the Crankshaft Position Sensor, did a relearn which involved driving it around for a while and checked for codes. No more codes found. So hopefully that was all it was.

Full-Timers · 11-03-2009, 10:38 PM

Quote:

Originally Posted by DriVer

Full Timers, I don't want you to commit to buying a part on my say so however your failure certainly sounds consistent with a failed TAC. Call Brazels and ask to talk to Jon. He might just be able to give you a little better feel for what you're experiencing.

Thanks for the tip DriVer. I did call Jon and he said to start with the Crankshaft Sensor. He said he sees more Crankcase sensors than TACs fail.

mfire1339 · 11-03-2009, 11:21 PM

I think I'll put my spare CPS in the MH. Won't do much good in the garage.

Mike

TXiceman · 11-04-2009, 02:36 AM

Sounds like the 8.1L folks maybe buying up all of the old Ford CPS (Cam shaft Positions Sensors). Ford had to do something with them after the recall......he he he.

Ken

Full-Timers · 11-04-2009, 04:05 PM

Quote:

Originally Posted by mfire1339

I think I'll put my spare CPS in the MH. Won't do much good in the garage.

Mike

The connector on the new one was different than the old one and they had to cut the old connector off and splice in the new one. They look very similar. You might want to check into that or just carrying around a sensor might not do you any good.

Full-Timers · 11-04-2009, 04:18 PM

I’m not so sure the old one was bad. What they pulled out the old one they said there was a lot of metal on the end of it. I am thinking this is the normal metal that floats around in a crankcase and enough stuck to the sensor that it distorted, reduced, or stopped the signal from getting through and freaked out the PCM.
Anyway we just completed a 300 mile trip across the California desert with no problems so I am a happy camper.