no spark on lm7, HELP!
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Ok so here is the deal. 5 volts to the map sensor. got a noid light, no pulsing while cranking. Checked to make sure the noid light was good on my silver ado and it is. Checked the CKP sensor. It had 12 volts on the red wire and 11 on the yellow with black tracer! This is the ground wire correct? I checked the power for that pin at the harness and it doesn't have power at the computer. When I plug the harness into the ECM and check it with a volt meter the yellow with black tracer has power. I'm gonna grab lunch but I'm thinking short in the wiring harness where these 2 wires have rubbed through and are now touching.
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False alarm on the CKP sensor wires conducting between each other. My thumb was touching the leads for the volt meter. With the harness plugged into the ECM I get 11 volts on the power wire and 9-10 on the ground lead (yellow w black tracer). the three wires are free of any shorts. there is no pulsing at the injectors. Does anybody know how to check and see if the crank sensor I just installed was bad out of the box?
Checked the CKP sensor. It had 12 volts on the red wire and 11 on the yellow with black tracer! This is the ground wire correct? I checked the power for that pin at the harness and it doesn't have power at the computer. When I plug the harness into the ECM and check it with a volt meter the yellow with black tracer has power.
Sounds like you may have the same open wire as I had.
Don't get too hung up on the ground aspect, although there would have to be a ground to cause the 11 volts to be significant.
As you have said, the 11 volts is seen at the CKP sensor plug, but is not seen on the same wire at the ECM.
If you don't see any crosses between the CKP wires, you can easily bypass that blk/yel wire by running a temporary wire from the CKP harness end, directly to the ECM.
This should prove the trouble (if that is indeed the problem).
Good luck!
Just want to revisit this...you mentioned that the 11volts seen on the yel/blk at the CKP sensor, is not seen at the corresponding pin of the harness at the ECM (with the harness disconnected, I presume?)
I'm not sure now if that's what you meant. If so, this is a trouble.
I'm not sure now if that's what you meant. If so, this is a trouble.
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If i undo the harness and check the pins on the ECM it doesngt have power but when I plug the harness in and put the voltmeter into the yello w black tracer wire and check it it does if I remember correctly. I checked all 3 wires and they have conductivity. 5 volts at the map and no pulse at the injectors
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I have power to the CKP sensor and MAP. All wires on these circuits are good when checked one by one. New cam and crank sensors. No spark or injector pulse... I'm losing my mind
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With the harness plugged into the ECM I get 11 volts on the power wire and 9-10 on the ground lead (yellow w black tracer). the three wires are free of any shorts. there is no pulsing at the injectors. Does anybody know how to check and see if the crank sensor I just installed was bad out of the box?
I would doubt the second crank sensor is bad, but not 100 percent sure, I have seen wierder.
Checked the CKP sensor. It had 12 volts on the red wire and 11 on the yellow with black tracer! This is the ground wire correct? I checked the power for that pin at the harness and it doesn't have power at the computer. When I plug the harness into the ECM and check it with a volt meter the yellow with black tracer has power.
I have a commitment today. If I get back and you're still looking, I'll verify this.
At the ECM, with the harness disconnected, there is a ground on pin 22/blue connector (in my case), which is the ECM pin that terminates the blk/yel wire from the CKP sensor.
Last edited by gMAG; Oct 2, 2011 at 10:02 PM.
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Ok so now I'm getting it... On my harness (painless) at the CKP plug I have a RED, a Yellow w/ Black Tracer, and a YELLOW. I dont know why I didn't think that it needs a ground to operate and that the ground lead wouldn't switch polarity. My bad. I don't fully understand the way the ECM reads the CKP sensor. So I should have a ground going into that CKP sensor. I can check this right now. I'll put a test light on it and see if it grounds. Should it ground on the signal wire as well or no?
Checked to make sure the noid light was good on my silver ado and it is. Checked the CKP sensor. It had 12 volts on the red wire and 11 on the yellow with black tracer! This is the ground wire correct? I checked the power for that pin at the harness and it doesn't have power at the computer. When I plug the harness into the ECM and check it with a volt meter the yellow with black tracer has power. I'm gonna grab lunch but I'm thinking short in the wiring harness where these 2 wires have rubbed through and are now touching.
1)Red wire=12v from the ECM toward >>>>the CKP sensor. This is your operating voltage.
2)Ground from ECM. This ground causes a complete circuit for the Red 12v batt, back to the ECM.
3) Signal (5v or so). This is your Crank signal. This lead would also require a ground from the ECM to complete the sig circuit.
This description I copied from a sensor tester booklet. Your CAM position sensor operates the same way.
..."Two wires supply batt & grnd. The 3rd wire carries the sensor sig back to the ECM. A small air gap separates the sensor and magnet. The magnet field causes the Hall switch (CKP) to turn on & send out a low volt sig. If a metal strip (reluctor wheel) is placed in the gap, it will block the magnetic field from reaching the Hall device. This causes the Hall switch to turn off & send a high volt sig (toward the ECM) out on the sig wire.
The metal strips (blades) are part of a disk or cup attached to a rotating component such as the crank or cam. As the blades pass through the sensor gap, the sig volt will switch from high to low creating a series of pulses.
The computer determines speed of rotation by measuring how fast pulses appear."
I didn't want you to get too hung up on all of this and send you in the wrong direction. If the ECM doesn't give you the "RPM" readout from a scan, it would mean that your CKP sensor sig can be seen by the ECM.
An ocilloscope can also read the pulses off of the signal lead.
You might also be able to 'see' pulses with a digital multimeter that has a capture device.
Last edited by gMAG; Oct 3, 2011 at 12:06 PM.
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OK. I'm gonna check this as soon as I get home. All the wires if I remember had some kind of voltage. Also if i remember correctly the yellow w black tracer was in the middle so according to the literature it should be the signal wire which means it would be appropriate for it to have voltage but I'll have to check when I'm home.
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also... If i had someone slowly turn the motor over with a breaker bar I should be more easily able to see this high voltage/low voltage signal put out by the crank sensor correct? and is it posible that the cam sensor is playing a part in this or is it irrelevant at this point?
also... If i had someone slowly turn the motor over with a breaker bar I should be more easily able to see this high voltage/low voltage signal put out by the crank sensor correct? and is it posible that the cam sensor is playing a part in this or is it irrelevant at this point?
However, I don't know if the sensor when triggered, will give off only a momentary signal (such as in milli-sec). There's a thread around here in which someone provided an ocilloscope view of the CKP pulse, but I think it was done at operating speed, which would cause the pulse to appear of short duration.
Cam sensor..This one can be checked the same as the CKP. Anything is possible with EFI, but since you have the symptoms of a missing crank signal, I would tend to go after that, first.
Someone needs to invent a device where car owners can plug into the OBDII
connector, and have the ECM read over a cellphone.
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ok so check this out... With the harness PLUGGED IN at the ECM and the CKP SENSOR UNPLUGGED... I get a voltage reading coming out of the ECM into the center signal wire. I have 12v on the red one on the left and ground on the solid yellow wire on the right when checked at the plug for the CKP Sensor. There are no shorts in the wires. All the pieces of the puzzle are starting to fit together. There is power feeding out of the ECM to the signal wire. After all of the info you guys have given me this is the culprit correct? Something in the ECM is feeding power to the signal wire rather than the CKP sensor feeding a signal to the ECM.
