Crankshaft Position Sensor (car died, no start)
04-14-2007 | 01:12 AM
#1
Crankshaft Position Sensor (car died, no start)
Hi folks,
Crankshaft Position Sensor (CPS) failure seems to be a common occurence among SS Supercharged models of all years (05--07), so I thought I would make a post summarizing the problem so that others can be wary of it and possibly take action before this happens to them.
Crankshaft Position Sensor
Q: What is it?
A: "The crankshaft position sensor is designed to record the rate at which the crankshaft is spinning. This sensor consists of a toothed metal disk mounted on the crankshaft and a stationary detector that covers a magnetic coil that the current passes through. As the metal teeth move past the coil, its magnetic field is disturbed. This causes a stream of pulses in the current. The computer can calculate the crankshaft's speed from the frequency of the pulses." - Innerauto.com
Short Answer: It is an electrical sensor that monitors the rotation of your crankshaft. If the cars computer cant determine that, it will essentially get confused and shut off the engine to prevent catastrophic failure.
Q: How can it fail?
A: Being an electrical device, a short in the electrical system can momentarily disable the sensor, usually leaving a partial or permanent loss of function. If this occurs, the car will fall flat on its face as the computer shuts the engine off, yet you will retain full accessory power. You will likely be inclined to assume your starter has failed, but most of the time that is not the case. When the CPS gets tripped by a disruption in electrical current, it is possible for it to resume regular function after 10 to 15 minutes of powering the car off, as evidenced by cobaltss.net member accounts. It can only be assumed that during this time all residual electricity is dissipated, and the car is able to function normally. As with other electrical devices though, once an event such as this occurs, it can affect the reliability and lifespan of the sensor. For this reason it is advisable you replace it. The procedure is covered under warranty. Unfortunately there is no Technical Service Bulletin or Recall for this issue yet, so its not an "official" problem with our cars.
Short Answer: If it shorts out once, you can only hope it doesn't happen again. Replace it under warranty.
Q: Is there a code indicating that the CPS has failed?
A: Yes, but in some cases (such as mine), the code did not come up, so it is not 100% reliable to depend on it. The code for CPS failure is P0335.
Q: Am I more prone to experience CPS failure if I have high mileage or extensive modifications to my motor?
A: No you are not. There have been numerous reports of CPS failure from people with 100% stock vehicles with under 5000 miles on them, to those with performance upgrades such as GM Stage 2 and over 15,000 miles.
Short Answer: It doesn't matter what mods or how many miles you have. You can experience CPS failure at any time.
Q: Does weather affect the likelihood of CPS failure?
A: While you MAY be more prone to CPS failure in the colder months where static electricity is more of a danger, there have been accounts of this happening in warm, humid climates as well.
Short Answer: Rain or shine, CPS failure can still occur.
Replacement
If you find yourself the victim of CPS failure and your car is still under warranty, rest assured replacement is covered.
Once diagnosed, your dealer will have to order the part, and as evidenced by user accounts, this can be a lengthy waiting period. Depending on your situation, you may not be able to be without your car for more than a few days, and the average wait time for the dealership to receive and install this part ranges from 1--2 weeks. Average time to install the part once received is one to two days.
Now imagine this happens to you (cross your fingers it doesn't), wouldn't it be nice to have the part on-hand to present to the dealer, thus vastly minimizing down-time? Sure, you might surprise the dealer by already having the part, maybe even raise some suspicion, but then you could just print out this post and show them you're not a paranoid wacko that hordes engine sensors in a shoebox somewhere :P.
Here is the part number for the CPS: 12789959 @ GMPartsdirect.com
As you can see, the $14 price tag is well worth the peace of mind that should this ever happen to you, you wont have to wait as long to get your car back because you will be able to provide the dealership with the part instead of waiting for them to order it with the risk of it being on back order (as it was in my case).
Cobaltss.net Member Accounts
In case you're not sure that your problem is the CPS, you can read through the following cobaltss.net member accounts of their experiences. These threads were primarily assembled by searching for the phrase "car died", "CPS", "crankshaft", "crank shaft", and "crankshaft position". The year, model, and whether each person had stage 2 or not is documented:
Car died at full throttle 1st gear - RonSS (2006 Cobalt SS/SC, GMPP Stage 2)
Car died. - Pyros777 (2007 Cobalt SS/SC, Stock)
Car died!!! - Screamin! (2006 Cobalt SS/SC, GMPP Stage 2)
Car died todAY - Joewit
Car Died Last Night!!!! - BADZSS06 (2006 Cobalt SS/SC, GMPP Stage 2)
My car just died!! - mikey80z (2006 Cobalt SS/SC, GMPP Stage 2)
No Start - bdwarr6 (2005 Cobalt SS/SC)
uhh... what happened? - SKDR112888 (2007 Cobalt SS/SC)
P0335 Crankshaft Postion Sensor A Circuit Malfunction - sneaky (2005 Cobalt SS/SC)
(Hopefully those are enough links to get the general idea of how to detemine whether your problem is the CPS or not)
Other Reading
Since the CPS is nothing new to cars in general, we can learn to diagnose this issue by reading what other people have to say about it. Here is a link I found helpful while researching the CPS: http://www.misterfixit.com/crnksnsr.htm
////////////////////////////////////////////
Hope this thread has been helpful.
cps crank shaft crankshaft position sensor car died dead no wont won't start stall
Crankshaft Position Sensor (CPS) failure seems to be a common occurence among SS Supercharged models of all years (05--07), so I thought I would make a post summarizing the problem so that others can be wary of it and possibly take action before this happens to them.
Crankshaft Position Sensor
Q: What is it?
A: "The crankshaft position sensor is designed to record the rate at which the crankshaft is spinning. This sensor consists of a toothed metal disk mounted on the crankshaft and a stationary detector that covers a magnetic coil that the current passes through. As the metal teeth move past the coil, its magnetic field is disturbed. This causes a stream of pulses in the current. The computer can calculate the crankshaft's speed from the frequency of the pulses." - Innerauto.com
Short Answer: It is an electrical sensor that monitors the rotation of your crankshaft. If the cars computer cant determine that, it will essentially get confused and shut off the engine to prevent catastrophic failure.
Q: How can it fail?
A: Being an electrical device, a short in the electrical system can momentarily disable the sensor, usually leaving a partial or permanent loss of function. If this occurs, the car will fall flat on its face as the computer shuts the engine off, yet you will retain full accessory power. You will likely be inclined to assume your starter has failed, but most of the time that is not the case. When the CPS gets tripped by a disruption in electrical current, it is possible for it to resume regular function after 10 to 15 minutes of powering the car off, as evidenced by cobaltss.net member accounts. It can only be assumed that during this time all residual electricity is dissipated, and the car is able to function normally. As with other electrical devices though, once an event such as this occurs, it can affect the reliability and lifespan of the sensor. For this reason it is advisable you replace it. The procedure is covered under warranty. Unfortunately there is no Technical Service Bulletin or Recall for this issue yet, so its not an "official" problem with our cars.
Short Answer: If it shorts out once, you can only hope it doesn't happen again. Replace it under warranty.
Q: Is there a code indicating that the CPS has failed?
A: Yes, but in some cases (such as mine), the code did not come up, so it is not 100% reliable to depend on it. The code for CPS failure is P0335.
Q: Am I more prone to experience CPS failure if I have high mileage or extensive modifications to my motor?
A: No you are not. There have been numerous reports of CPS failure from people with 100% stock vehicles with under 5000 miles on them, to those with performance upgrades such as GM Stage 2 and over 15,000 miles.
Short Answer: It doesn't matter what mods or how many miles you have. You can experience CPS failure at any time.
Q: Does weather affect the likelihood of CPS failure?
A: While you MAY be more prone to CPS failure in the colder months where static electricity is more of a danger, there have been accounts of this happening in warm, humid climates as well.
Short Answer: Rain or shine, CPS failure can still occur.
Replacement
If you find yourself the victim of CPS failure and your car is still under warranty, rest assured replacement is covered.
Once diagnosed, your dealer will have to order the part, and as evidenced by user accounts, this can be a lengthy waiting period. Depending on your situation, you may not be able to be without your car for more than a few days, and the average wait time for the dealership to receive and install this part ranges from 1--2 weeks. Average time to install the part once received is one to two days.
Now imagine this happens to you (cross your fingers it doesn't), wouldn't it be nice to have the part on-hand to present to the dealer, thus vastly minimizing down-time? Sure, you might surprise the dealer by already having the part, maybe even raise some suspicion, but then you could just print out this post and show them you're not a paranoid wacko that hordes engine sensors in a shoebox somewhere :P.
Here is the part number for the CPS: 12789959 @ GMPartsdirect.com
As you can see, the $14 price tag is well worth the peace of mind that should this ever happen to you, you wont have to wait as long to get your car back because you will be able to provide the dealership with the part instead of waiting for them to order it with the risk of it being on back order (as it was in my case).
Cobaltss.net Member Accounts
In case you're not sure that your problem is the CPS, you can read through the following cobaltss.net member accounts of their experiences. These threads were primarily assembled by searching for the phrase "car died", "CPS", "crankshaft", "crank shaft", and "crankshaft position". The year, model, and whether each person had stage 2 or not is documented:
Car died at full throttle 1st gear - RonSS (2006 Cobalt SS/SC, GMPP Stage 2)
Car died. - Pyros777 (2007 Cobalt SS/SC, Stock)
Car died!!! - Screamin! (2006 Cobalt SS/SC, GMPP Stage 2)
Car died todAY - Joewit
Car Died Last Night!!!! - BADZSS06 (2006 Cobalt SS/SC, GMPP Stage 2)
My car just died!! - mikey80z (2006 Cobalt SS/SC, GMPP Stage 2)
No Start - bdwarr6 (2005 Cobalt SS/SC)
uhh... what happened? - SKDR112888 (2007 Cobalt SS/SC)
P0335 Crankshaft Postion Sensor A Circuit Malfunction - sneaky (2005 Cobalt SS/SC)
(Hopefully those are enough links to get the general idea of how to detemine whether your problem is the CPS or not)
Other Reading
Since the CPS is nothing new to cars in general, we can learn to diagnose this issue by reading what other people have to say about it. Here is a link I found helpful while researching the CPS: http://www.misterfixit.com/crnksnsr.htm
////////////////////////////////////////////
Hope this thread has been helpful.
cps crank shaft crankshaft position sensor car died dead no wont won't start stall
Last edited by Pyros777; 04-21-2007 at 07:39 PM.
04-14-2007 | 02:14 AM
#4
Senior Member
Joined: 01-25-06
Posts: 4,309
Likes: 0
From: Ellsworth AFB, South Dakota (from Mechanicsburg, Pennsylvania)
The CPS failing was also a common problem on the generation Wrangler I used to own(YJ, 87-95). It failed on me out in the middle of Farmingdale while I was out wheeling. I stalled it and it wouldn't start back up...
I even have a video of what it sounds like when it does go out in my post. :P Good info to know.
05-21-2007 | 02:58 PM
#9
Premium Member
Joined: 07-04-05
Posts: 730
Likes: 1
From: No where man
Most of the problems with the CKP signal have been attributed to a poor electrical connection either at the CKP sensor or up at the ECM/PCM. (although not surprisingly replacing the sensor often repairs the connection as well) Sometimes (rarely) the seal around the magnet itself allows the sensor to take on engine oil, which can eventually short out the windings. If you unplug the sensor and you see engine oil within the connection, it's likely not far from failure. But it's not like this is something "chronic" on the LSJ or anything.
The "quick check" for testing the CKP signal is making it to the ECM/PCM is to observe for consistent RPM values while cranking the engine on a scan tool (or Aeroforce gage) Detailed testing can also be performed at the sensor itself. LSJ CKP sensor resistance should be betwen 600-1100 ohms and an AC voltage signal of a few hundred mill-Volts can be measured across the sensor circuit while cranking.
It only takes about 20-30 minutes to change the CKP sensor on the Ecotec, as the starter will generally have to be removed to access it- as it probes through a hole in the LH side block just below the oil filter housing(see pic) and the Crankshaft Variation Relearn will need to be performed whenever it's replaced.
Not sure how the OP figures a CKP sensor failure results in a condition that would have you "be inclined to assume your starter has failed" when the engine will CRANK just fine, -it just wont start as there will be no fuel/spark delivered . This is because the triggering of the injectors and the coils is syncronized to the 58X signals created by the CKP.
HTH
Wop
The "quick check" for testing the CKP signal is making it to the ECM/PCM is to observe for consistent RPM values while cranking the engine on a scan tool (or Aeroforce gage) Detailed testing can also be performed at the sensor itself. LSJ CKP sensor resistance should be betwen 600-1100 ohms and an AC voltage signal of a few hundred mill-Volts can be measured across the sensor circuit while cranking.
It only takes about 20-30 minutes to change the CKP sensor on the Ecotec, as the starter will generally have to be removed to access it- as it probes through a hole in the LH side block just below the oil filter housing(see pic) and the Crankshaft Variation Relearn will need to be performed whenever it's replaced.
Not sure how the OP figures a CKP sensor failure results in a condition that would have you "be inclined to assume your starter has failed" when the engine will CRANK just fine, -it just wont start as there will be no fuel/spark delivered . This is because the triggering of the injectors and the coils is syncronized to the 58X signals created by the CKP.
HTH
Wop
Last edited by WopOnTour; 06-12-2007 at 05:31 PM.
05-21-2007 | 03:20 PM
#10
The assumption of the starter failure came from the onstar diagnostic that was performed within minutes of the sensor failing. Unfortunately I dont know the code, but the person on the line said the diagnostic indicated there was a starter failure. Its possible the code for the starter came up due to the fact that the diagnositc was run while the engine was off.
In any case, thanks for chiming in with that great info!
In any case, thanks for chiming in with that great info!
06-12-2007 | 10:27 AM
#11
Member
Joined: 07-05-06
Posts: 244
Likes: 0
From: DFW,TX Denton-HM Dallas-WK
My totally stock car 06 SS/SC has been sitting at the dealership for the past 11 days due to a CPS failure (waiting on parts). The sensor had been replaced 2 days before that. Long story short, GM is installing a new crankshaft and assorted parts. They said my crankshaft had some play in it causing the CPS sensor to not be able to get a reading. I dont know if this is a common occurance as well or if Im a rarity but I thought I'd throw it out there for those of you that have experienced it repeatedly.
06-12-2007 | 01:10 PM
#12
Premium Member
Joined: 07-04-05
Posts: 730
Likes: 1
From: No where man
I would say very rare and even (with no disrespect) question whether they are providing you with 100% accurate information. I've measured dozens of Ecotec crankshafts (some with high milage) and never seen the endplay more than maybe .012-.013" (max is .018")which even at maximum-certainly wouldnt be enough to throw off a VR type CKP sensor, that is machined to almost perfect alignment.
I guess if they are replacing the crank, they've already replaced the thrust bearing? (#2 main) or maybe they are concerned about the CKP reluctor itself maybe?? (which still doesnt make sense as the reluctor wheel are serviced seperately)
I guess what I'm saying is I cant help but think that there's something electrical that they've missed. Maybe ask them what AC voltage levels they measure AT THE SENSOR vs. AT THE PCM while cranking...
Wop
I guess if they are replacing the crank, they've already replaced the thrust bearing? (#2 main) or maybe they are concerned about the CKP reluctor itself maybe?? (which still doesnt make sense as the reluctor wheel are serviced seperately)
I guess what I'm saying is I cant help but think that there's something electrical that they've missed. Maybe ask them what AC voltage levels they measure AT THE SENSOR vs. AT THE PCM while cranking...
Wop
06-12-2007 | 06:21 PM
#13
Member
Joined: 07-05-06
Posts: 244
Likes: 0
From: DFW,TX Denton-HM Dallas-WK
I would say very rare and even (with no disrespect) question whether they are providing you with 100% accurate information. I've measured dozens of Ecotec crankshafts (some with high milage) and never seen the endplay more than maybe .012-.013" (max is .018")which even at maximum-certainly wouldnt be enough to throw off a VR type CKP sensor, that is machined to almost perfect alignment.
I guess if they are replacing the crank, they've already replaced the thrust bearing? (#2 main) or maybe they are concerned about the CKP reluctor itself maybe?? (which still doesnt make sense as the reluctor wheel are serviced seperately)
I guess what I'm saying is I cant help but think that there's something electrical that they've missed. Maybe ask them what AC voltage levels they measure AT THE SENSOR vs. AT THE PCM while cranking...
Wop
I guess if they are replacing the crank, they've already replaced the thrust bearing? (#2 main) or maybe they are concerned about the CKP reluctor itself maybe?? (which still doesnt make sense as the reluctor wheel are serviced seperately)
I guess what I'm saying is I cant help but think that there's something electrical that they've missed. Maybe ask them what AC voltage levels they measure AT THE SENSOR vs. AT THE PCM while cranking...
Wop
I am a little apprehensive that some grimlins may sneak in there while its apart, I hope this isn't an omen of more problems down the road for me. Ive had zero problems with the car until this happened. I can ask next time I talk with them what the measured endplay was and for a more indepth explanation. I havent modded the car at all now Im thinking that maybe I shouldnt.
06-12-2007 | 06:46 PM
#14
Senior Member
Joined: 10-31-06
Posts: 2,251
Likes: 0
From: O-town
wow mother ****** i searched and this didnt come so i brought back a dead thread and am gonna get nothing but ****... Happened to my car today second time supposedly it was fixed the first time. AAAAAAAAAAHHHHHH!!!!!!!!!!!!!!!!
And hopefully everyone of you gave him rep points for this ****!!!!!
And hopefully everyone of you gave him rep points for this ****!!!!!
Last edited by DaREDss; 06-12-2007 at 06:46 PM. Reason: Automerged Doublepost
10-31-2008 | 01:32 AM
#16
New Member
Joined: 11-16-07
Posts: 81
Likes: 0
From: Frederick, Maryland
I just hit this Tuesday. I had to have the car towed via AAA. Car was at Criswell Chevrolet/Gaithersburg, Maryland. They told me the car started fine, and the code history was - P0335 Crank Pos Sensor Circ Error. They - "Inspected position sensor and wiring and found no problems". Car was road three separate times for 10 miles each and returned to me with - no trouble found. I drove it a bit hard on the way home and had no issues. Hmmm....
This forum and post is very helpful. thx
This forum and post is very helpful. thx
11-02-2008 | 01:13 PM
#18
11-02-2008 | 01:46 PM
#21