Topic: GM crank sensor voltage (Read 10107 times)

PhilStubbs · « **on:** July 12, 2010, 12:38:56 PM »

I am messing with a 96 blazer with a 4.3l v6. Some redneck tried to fix the transmission and now it doesn't run. If I crank it enough it gets a crank sensor code and watching with my scanner it shows no rpm signal. I probed the wire at the ecu with someone cranking it and got .2v in a rhythmic on/off pattern. I have had very limited help having someone to crank while I test so that's about as far as I have gotten. With the key on and no cranking I got 10v at the sensor. Seems like a broken wire to me but I'm just wondering what the voltage is supposed to be. I would assume 5v but I got 10v from the cam sensor while cranking.

Joseph Davis · « **Reply #1 on:** July 12, 2010, 02:12:06 PM »

"A blah blah blah code" means exactly jack and shit on an OBD2 vehicle. Tell me which specific code you have.

PhilStubbs · « **Reply #2 on:** July 12, 2010, 03:20:29 PM »

I will recheck it tonight and let you know. I dont remember the exact wording or the pxxxx number.

PhilStubbs · « **Reply #3 on:** July 12, 2010, 06:29:11 PM »

Code P0336 CKP sensor circuit perf.

snm95ls · « **Reply #4 on:** July 12, 2010, 06:41:39 PM »

I can't say I have ever replaced a crank sensor on a 96+ W motor and I have seen quite a few. You might want to check and make sure the wiring harness didn't get pinched between the block and the harness.

Also:

Quote

Circuit Description
The Crankshaft Position (CKP) sensor sends a reference signal to the Vehicle Control Module (VCM) in order to indicate the crankshaft position and the RPM so that the VCM can determine when to pulse the ignition coil, the fuel injectors, and the control ignition timing. This is a type D DTC.

Conditions For Setting The DTC
The Following Conditions will set the DTC:

* The Crankshaft Position sensor signal is missing for at least 0.5 seconds.
* The engine cranking and the VCM receives 4 or more CAM Shaft Position signals without a Crankshaft Position sensor signal.

Action Taken When The DTC Sets
The VCM stores the DTC to the history if the VCM detects an intermittent problem.

Conditions For Clearing The MIL/DTC
A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40Â°F from the start-up coolant temperature and the engine coolant temperature exceeds 160Â°F during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids
A poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation may cause an intermittent.

Thoroughly check any circuitry, that is suspected as causing the intermittent complaint, for the following conditions:

* Backed out terminals.
* Improper mating.
* Broken locks.
* Improperly formed or damaged terminals.
* Poor terminal to wiring connections.
* Physical damage to the wiring harness. Refer to Intermittents. See: Symptom Related Diagnostic Procedures\Intermittent Condition

Test Description
The numbers below refer to the step numbers on the diagnostic table.

2. This step determines if the VCM is receiving the Crankshaft Position sensor pulses.
3. This step checks the ignition feed circuit to the Crankshaft Position sensor.
4. This step checks the Crankshaft Position sensor low circuit.
5. This step checks the Crankshaft Position Sensor.

HTH

PhilStubbs · « **Reply #5 on:** July 12, 2010, 07:10:45 PM »

well, the story changes a little. the shitty colorings on the wires had me probing the wrong ones. i found a pin diagram, unhooked the plug and checked, the connection from crank sensor to ecu is perfectly fine. but i am getting 11v on the signal wire. seems like a lot to me.

i did follow the harness from the sensor to the ecu and it seems fine. i dont see any sign of damage

PhilStubbs · « **Reply #6 on:** July 12, 2010, 08:12:40 PM »

also, just to add, i finally got someone to crank while i probed the signal wire. i get 3.5v then 4v in a steady pattern while cranking. that number sounds right to me, but after a solid hour of searching i cant find what it is actually supposed to be.

snm95ls · « **Reply #7 on:** July 12, 2010, 11:20:34 PM »

Quote from: SecksyPeePee on July 12, 2010, 07:10:45 PM

well, the story changes a little. the shitty colorings on the wires had me probing the wrong ones. i found a pin diagram, unhooked the plug and checked, the connection from crank sensor to ecu is perfectly fine. but i am getting 11v on the signal wire. seems like a lot to me.

i did follow the harness from the sensor to the ecu and it seems fine. i dont see any sign of damage

You are getting 12V on the signal wire when the CKP is disconnected, or what? Kind of have to be more descriptive.

According to the diagnostic charts, they essentially want you to check the continuity of the wires going between the PCM and the CKP, and of course check for shorts to ground and B+ where there shouldn't be. After that, the charts want you to check the duty cycle with the engine running. Obviously in order to do this you are going to have to back-probe, use a bed of nails, or make some jumpers. Basically if the duty cycle is less than 40%, then the CKP is faulty.

If I were a betting man, I would say it needs a new CKP if your wiring is intact.

Joseph Davis · « **Reply #8 on:** July 12, 2010, 11:24:12 PM »

Quote from: snm95ls on July 12, 2010, 11:20:34 PM

Quote from: SecksyPeePee on July 12, 2010, 07:10:45 PM
well, the story changes a little. the shitty colorings on the wires had me probing the wrong ones. i found a pin diagram, unhooked the plug and checked, the connection from crank sensor to ecu is perfectly fine. but i am getting 11v on the signal wire. seems like a lot to me.

i did follow the harness from the sensor to the ecu and it seems fine. i dont see any sign of damage

You are getting 12V on the signal wire when the CKP is disconnected, or what? Kind of have to be more descriptive.

According to the diagnostic charts, they essentially want you to check the continuity of the wires going between the PCM and the CKP, and of course check for shorts to ground and B+ where there shouldn't be. After that, the charts want you to check the duty cycle with the engine running. Obviously in order to do this you are going to have to back-probe, use a bed of nails, or make some jumpers. Basically if the duty cycle is less than 40%, then the CKP is faulty.

If I were a betting man, I would say it needs a new CKP if your wiring is intact.

OK, your ability to understand and diagnose this shit has become more and more apparent in the last six months. What changed?

snm95ls · « **Reply #9 on:** July 12, 2010, 11:27:47 PM »

Quote from: Joseph Davis on July 12, 2010, 11:24:12 PM

OK, your ability to understand and diagnose this shit has become more and more apparent in the last six months. What changed?

I guess being back in the field helps a little.

$:-\$

PhilStubbs · « **Reply #10 on:** July 13, 2010, 07:00:06 AM »

All of my wire testing has been done with everything plugged it.

I got 12v on the signal wire with the key on, enine not running. With someone cranking it, I got 3.5v and 4v in a steady pattern as if the ckp sensor is working properly. I just don't know what it's supposed to be to compare my findings and any info on the Internet is garbage. It seems only retards own these things or the people that do know are very possessive of their info

t_cel_t · « **Reply #11 on:** July 14, 2010, 09:31:42 PM »

is this a vr or a hall effect sensor? how many wires going into it?

snm95ls · « **Reply #12 on:** July 14, 2010, 09:32:25 PM »

Quote from: t_cel_t on July 14, 2010, 09:31:42 PM

is this a vr or a hall effect sensor? how many wires going into it?

It is a hall effect.

PhilStubbs · « **Reply #13 on:** July 14, 2010, 10:20:29 PM »

Yes hall effect. 3 wires.

t_cel_t · « **Reply #14 on:** July 14, 2010, 10:44:35 PM »

well if there is 12v the power side of the sensor when its in the on position i would run a jumper wire strait from the battery to the sensor. it wont hurt it, obviously something is causing a drop-probably a rusty ground or something.

PhilStubbs · « **Reply #15 on:** July 15, 2010, 09:02:52 AM »

I'm getting good power into the sensor and a good ground at the sensor too. My concern is the signal coming out, there is no info online as to what that sensor should put out

Joseph Davis · « **Reply #16 on:** July 15, 2010, 09:14:21 AM »

Well, Scott, it's a Hall Effect sensor. It should put out a square wave. 0-5v or 0-12v is irrelevant if the ECM is looking for a ground-level logic signal.

Put a meter across the output and ground, monitor voltage. Slowly turn the crank by hand. You should be able to watch the voltage switch bak and forth.

PhilStubbs · « **Reply #17 on:** July 15, 2010, 11:31:17 AM »

That's what I have been saying. I'm getting 3.5v and 4v in a nice (as best as I can tell with a multimeter) square pattern

Joseph Davis · « **Reply #18 on:** July 15, 2010, 12:28:38 PM »

Seems pretty straightforward.

PhilStubbs · « **Reply #19 on:** July 15, 2010, 12:40:59 PM »

I have been through every bit of that. Ecu was replaced and programmed by the dealer and ckp sensor has been replaced twice. I have check all 3 wires from one end to the other with no sign of a problem. I am kind of leaning toward bad programming of the ecu at this point.

snm95ls · « **Reply #20 on:** July 15, 2010, 02:04:13 PM »

Heh, if you were local, I would snag the Tech 2 from work to take a look at it.

Have you back probed the signal pin at the PCM to see what the voltage is there?

You said you have checked the wires; Was this a visual inspection or what? Granted a system like this ought to have very little current running through the wires, but have you tried load testing the signal, B+, and ground wires?

PhilStubbs · « **Reply #21 on:** July 15, 2010, 02:39:11 PM »

I'm using a pretty nice Mac taskmaster for all of my scanner needs. Of course it's not dealer stuff, but it's not bad.

I probed the wire right at the plug to be sure I got the same reading at the sensor and ecu. I also unplugged both ends and checked it with a multimeter to make sure there were no broken spots in the wire

nock · « **Reply #22 on:** July 24, 2010, 03:52:04 AM »

sorry to go back to this, but it really sounds like the sensor isnt coupled to ground (the ECU sensor ground) somewhere.you said it got buschwacked by some redneck, are you sure that all the grounds in the harness are connected. i know that youve gone over this but its just that what you describe sounds just like an un-grounded hall sensor.

PhilStubbs · « **Reply #23 on:** July 24, 2010, 08:59:30 AM »

I have looked over every ground I can find and the ground wire going to the sensor itself shows good. I unplugged it and probed it in the connector. Is there some way that the body of the sensor is supposed to ground to the timing cover? I don't see anyway for that to happen

nock · « **Reply #24 on:** July 25, 2010, 11:54:14 PM »

a hall sensor hardly ever grounds to the motor.

another stupid question is: some hall sensors need pull-up resisters to work right so it might be good to just intercept the wires while your testing them (sorry i didnt read everything, dont know if you did this) also the hillbilly may have somehow cooked the pull-up resister.

if you get the same signals by intercepting the wire while its connected to the ecu and all the wires going to and from the ecu and sensor are good then id say your ecu is fried.

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Author Topic: GM crank sensor voltage (Read 10107 times)