02 Buick Lasbre

Nathan Owner/Technician Hillsboro, Ohio Posted   Latest   Edited  
Question
Driveability
2002 Buick LeSabre Custom 3.8L (K L36) 4-spd (4T65-E)—1G4HP54K42U269830
Crank / No Start
Camshaft Sensor Loosing Signal

Hello, everyone, I am looking for some guidance. What i have is a 02 Buick LeSabre that after it is driven for 15mins or so shut it off and the vehicle will not start. Found a cam signal code. scoped cam sure enough after it gets hot it will drop out shut it off and it will not restart. I hooked up the four leads to the 3 wires at the sensor and the 4th at the ICM on cam signal. From what i saw i figured a sensor would get it i tried 2 from 2 local parts store with no success. I found some info on the magnets getting weak on the cam gear. Is there anyway you can verify before replacing the magnet?

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Kenneth Owner/Technician
Searcy, Arkansas
Kenneth Default
 

About the no start. Check your injector signal, ignition spark and fuel pressure first I think. Then you can decide where to go from there.

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Martin Technician
Waukegan, Illinois
Martin Default
 

Agreed. If I recall the CMP sensor doesn't affect ignition system directly. Only the timing of the injectors.

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Edwin Diagnostician
Tuscaloosa, Alabama
Edwin Default
 

Be sure and look at harness good gets oil soaked when oil gets hot waa laa

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

Harness looks good no oil leaks

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Scott Owner/Technician
Brantford, Ontario
Scott Default
 

Try tap testing the crank sensor high failure rate back in the day , Will also mess with the ref voltage or scope the ckp when fault is present

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

checked crank sensor 18x 3x and cam sig at the ICM no problem crank sensor waveform

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Samuel Technician
Somers Point, New Jersey
Samuel Default
 

^^^ What Scott said....they were such a high failure rate that guys were replacing them with ZERO testing and they ended up being correct. Additionally, without having the vehicle in front of me, I thought only the crank sensor could cause a no start regarding inj. pulse and spark...been a while, keep us posted!

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George Diagnostician
Burnaby, British Columbia
George Default
 

I would try an oem cam sensor first

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

That's what i am thinking. There is a small difference in sensor height on these others from the parts store.

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Martin Technician
Waukegan, Illinois
Martin Default
   

Sounds like you can duplicate the problem fairly regularly. How about stabbing the 2 CKP signals, ICP and the CMP to the ICP and get it to stall again. OR I can read the post reply to Scott......

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

The problem is not stalling it is after he drives to some were like say the gas station. shuts it off pumps fuel and it will not restart. vehicle starts fine as long as it has a cam signal. verified by the scope. once signal drops shut the vehicle off and it will not restart till it cools off. I have scoped at the ICM pinout G, H, J, (G) CKP SIG (18X), (H) 3X CKP SIGNAL/SYNC, (J) CMP SIG. No…

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

Kind of a long shot. Heat does affect magnetism so how about, run it until the signal drops out, pull the sensor, direct a stream of shop air across the cam gear, put the sensor back and retest. Or run until it fails, pull the sensor, dip it in cool water, put the sensor back in and retest. What was the scenario when the AM sensors were tried?

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

i ran the vehicle this morning after installing the jumper leads down at the sensor. the engine got hot signal dropped. installed the other sensor and it ran for about 5mins then the signal dropped. to be clear the only thing letting me no the signal dropped is the scope there is no change in idle. I ordered a sensor from the dealer and it will be in tomorrow in the am.

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George Diagnostician
Burnaby, British Columbia
George Default
 

Always a good idea to use oem engine sensors when ever possible

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I wonder if something is grounding the signal wire? It’s odd to me that a new sensor would show the same symptom as the original. I know, AM sensors are suspect but to duplicate the symptom is suspicious.

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

i kinda thought that visual inspection of wire harness looks good. and i cut the signal wire right before the ICM to see if it was pulling it down and no change.

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I would have cut it near the sensor to eliminate the harness too. It occurred to me that the sensor pulls to ground in presence of the magnet. So a “failed” magnet would cause the signal to stay high. Since yours fails pulled low, it can’t be because the magnet is weak.

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

Hi Nathan. In addition to camshaft sensors and magnetic issues way back when, there were issues reported about loss of cam sensor signals, when the timing set had been replaced with aftermarket steel components instead of OEM spec components. The simplest route to take first is to see what is missing, fuel, spark or both and determine the course of action from there. The Ignition Control Module…

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

Thanks, martin yes there was a P0341. i did not try very hard to restart just a few seconds to verify the complaint. I'm going to try an OE sensor in the morning. the second sensor i tried failed erratically with forwarning dropouts in the waveform then just a complete drop. ill rescope things in the morning and get some more captures. i would think that if it was something to do with the…

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Update
 

Alight i went to the shop and grabbed a few new captures. when i get it hot shut it off and try to restart the injectors are not firing.

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Kenneth Owner/Technician
Searcy, Arkansas
Kenneth Default
 

Ohm test each injector while it is hot and not starting

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Paul Mechanic
Harvey, Illinois
Paul Default
 

What happens if once you lose cam signal/shorted and you remove sensor from engine while monitoring signal? Or connect one of the other sensors (cam) you have, does it jump back up to 7 volts? Does it show 7 volts on signal wire from icm even without sensor plugged in? I'm not near SI, ICM which supplies the 7 volts may be the issue. Base line your signal voltage with no sensor plugged in then…

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Default
 

I switched out sensors and it ran for about 5 mins then dropped the signal.. dealer did not get the oe sensor in this morning so i guess its waiting till monday.

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Paul Mechanic
Harvey, Illinois
Paul Default
 

Did you confirm if voltage on signal wire returned when you unplugged it? There is usually a bias voltage to signal wires to check circuit integrity.

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Greg Technician
University Place, Washington
Greg Default
 

What about when it acts up pull sensor out and run a magnet by it.

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Update
 

I tried a new OE sensor and no change. I saw no voltage on the signal wire when keys on and the problem is present. unplugged still no change. I tried running a magnet by the sensor no change in the waveform. I cut the wire for cam signal up by the ICM still no voltage on the signal wire coming out of ICM. kinda looking like ICM?

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I know what you stated makes sense to you but, not being there to see where you’re connected and what the voltage reading are, it’s hard for me to visualize and not get lost. When the problem is not present, there must be voltage on the signal wire. Opening the wire will indicate if the voltage is supplied by the ICM or the CMP. Lift the sensor so that it won’t be triggered. That will point to…

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Nathan Owner/Technician
Hillsboro, Ohio
Nathan Update
 

Thank you all for the Help with this situation. I apologize for the long delay. The way i approached this diag was completely wrong. I lacked a basic understanding of the circuits, a Rookie mistake. I completely disregarded the flow chart, thinking i had an understanding of what i was working on. What i found was There was not 5v on the signal wire at the CMP or at the ICM. However, there was 5v…

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I can personally attest, it won’t start without a cam signal. Paul Danner has a video of one that he taps a jumper on the cam signal to “create” a cam signal to start one.

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