2000 Volvo S40 Crankshaft position sensor light. I have changed the sensor and it still does the same thing. It will run 100% completely fine then all of a sudden when you pull up to a stop sign it will stall out. Right as it stalls out it seems like the car tries to surge forward and the Winter traction control light comes on along with the orange arrow. After the car stalls out, I start up the car and if I do not stay on the throttle it will just shut off again! So i'll rev it up and throw it in gear and it will work completely fine again till the next time it decides to freak out. I have hooked up a code reader and the only code it throws is Crankshaft positioning sensor. And the traction control lights eventually clear themseleves out until it acts up again. Has anyone had any problems of this sort?? Thank You

 

I also failed to mentioned that when the car is siting at idle it will rev up too about 2500rpm then come back down and go back up. When the ground is removed from the battery it will idle completely fine. I check both the grounds running to the frame and they are secured. Please help people, I am stumped!

 

I've heard bad stories about grounds coming loose while a car is running. Burning out headlights and computers and such. Your experience makes me wonder what voltage the alternator is putting out and how many volts the battery has when not charging.

I've never experienced your issues yet so all I have is questions and guesses. Not much help there.

 

Sorry I have not responded I was out of town. As soon as I get home this evening I will check and relay the reading to you. After a lot of research Im starting to believe it is the Idle air control sensor perhaps? But ill check the battery and altranator reading first.

 

Okay i Checked the battery 12.85 resting and 13.95 while running. I just bought this car with the light on and figured it would be an easy fix. Well today i actually drove the car for a while for the first time. The car is 100% great as long as i keep my foot on the throttle at stop signs/lights. All the service lights and check engine lights illuminate themselves after a while. But as soon as you dont hold on to the gas pedal at a light it dies right out and all the lights pop back on. It seems like an idle problem. I checked all the grounds, all the vacuum lines and everything seems fine. I think my next stance is to clean the egr or clean the idle air control valve?

 

more updates: When putting the scanner on it again today PO335 and PO336 Crank position sensor codes still popped up. Pending codes were the PO100 and PO400... Mass air flow and EGR. I cleaned the mass air flow but made no difference. But when i took the mass air flow off there was a plastic type screen that was broke off. Didn't seem like a crustal part of the MAF but am not sure. Next step is to clean the EGR. Have you encountered these similar codes with alike symptoms ever?

 

Sorry, I haven't had the codes myself. You can remove the IAC motor and control idle with your thumb over the square opening in the intake. You need a helper to start the car. You can hook the IAC up and watch it in your other hand as you control the idle air. Might tell you if the IAC is moving as it should. You'll need a new gasket as the green paper ones tear quite easy. You can always make a gasket from the sheets they sell at the autoparts store.

 

OK i checked the idle air control valve and it looked fine but replaced it anyways. IT still has the same symtoms. I have searched a couple other threads and do you think it could be the IAT Sensor? Or also do you think it could be a bad camshaft postion sensor thats making the car throw a crankshaft position sensor light?

 

I've read several other threads where a related system fails and this sets the crank position sensor failure message but I've never experienced this myself. With the two failure codes, PO335 and PO336, I would definitely make sure of the continuity of the CPS circuit before I started looking elsewhere.

Plus I hate throwing parts at a car! Done it many times though. Still hate it.

 

This may be a dumb question but where do i check for continuity? Do I unplug it and do it at the plug? Or do I have to stick my prongs into the wires that lead into the plug? Also is it going to have a low voltage constantly going to it? Thanks a lot Hudini I really appreciate it!

 

Normally the crank sensor is a simple magnet positioned close to a reluctor wheel with cut outs mounted on the crank. When the cut outs pass the magnet it generates a signal that the ECM can detect. Same with the cam sensor. What I was mainly suggesting was trace the electrical cable by hand to make sure it did not get pinched or burnt or otherwise damaged, all the way to the ECM if you can. I don't think there is any voltage from the ECM in the cable. I'm totally guessing here, just trying to give suggestions.

Here is a picture of the reluctor wheel on the exhaust cam:

 

Well it ended up being what Houdini said. The senor wasnt grounding out. There were 3 bolts on the bell housing that were finger tight and two others that werent even there. Once the bolts were tightingened and installed the other two, she now runs like a top! Just thought I would follow up with the solution unlike the other 90% of the posts that end with nothing! Thanks Houdini!!