Another CPS thread, Brand new CPS, no start
01-30-2018, 02:36 PM
#1
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Another CPS thread, Brand new CPS, no start
Hey All,
I know CPS's have been covered a thousand times, but I cannot seem to find the answer I'm looking for.
The problem:
Jeep died a while ago (cps failed), so I ordered a new one and installed it this morning, went to fire it up and no start. None of the gauges are reading out, odometer doesn't show anything, the only thing that happens when the key is in the start position is the starter is spinning. The new cps is a crown automotive replacement (part no. 56027866AE) so I believe is the correct sensor for a '99 (early 1999).
From what I understand I need to test the voltage of the new sensor to see if it is faulty, but am not sure how? I'm guessing the sensor is bad out of the box, but don't want to make that assumption until I test it.
Thanks in advance
I know CPS's have been covered a thousand times, but I cannot seem to find the answer I'm looking for.
The problem:
Jeep died a while ago (cps failed), so I ordered a new one and installed it this morning, went to fire it up and no start. None of the gauges are reading out, odometer doesn't show anything, the only thing that happens when the key is in the start position is the starter is spinning. The new cps is a crown automotive replacement (part no. 56027866AE) so I believe is the correct sensor for a '99 (early 1999).
From what I understand I need to test the voltage of the new sensor to see if it is faulty, but am not sure how? I'm guessing the sensor is bad out of the box, but don't want to make that assumption until I test it.
Thanks in advance
01-30-2018, 02:56 PM
#2
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Just replaced mine with a Mopar one that was that part # in my '00. The test did not work for me but I believe I was experiencing thermal failure cause the Jeep would start right back up after it stalled.
01-31-2018, 12:42 PM
#3
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Thanks for the link to the video, I've now tested it and am getting a resistance of 20,000 ohms, not sure if that means it is faulty or not, the old sensor was reading out a resistance of 5,000 ohms
01-31-2018, 01:44 PM
#4
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I've been trying to come up with a simple way to contribute to the questions here.
On a 3 wire CPS as you find in the Jeep, 2 wires are used to provide a power circuit to the sensor which is used to power a small electromagnet that produces changes when other metal comes near it. These changes are then communicated as voltage fluctuations on the 3rd wire (usually called the signal wire) to the PCM (engine computer).
What this means is that testing a CPS with a multimeter, despite the posts and videos that make it seem otherwise, is only testing that these wires are in good shape and are not damaged or otherwise failing within the sensor. So if there is a continuity problem with the wires, they can help demonstrate that the CPS is bad and needs to be replaced. So these tests can "rule-in" that the CPS is a problem. However, because these tests do not concern the signal quality being communicated to the PCM, they can not "rule-out" the CPS as being a problem.
The trouble being, that even after doing the meter test, the CPS could still be the problem. And the failure modes of CPS often are just like that, such that the wires are fine but because of the degradation of the sensor it is no longer providing a useful or recognized signal to the computer.
CPS signals are tested using a scope in order to see the pattern of the signal. Typically scope is set up to measure both the camshaft position sensor and the crankshaft position sensor, because not only must their signals be appropriate, they must be appropriate in relationship to each other. If any of these these things are not as they should be, the computer will not initiate ignition (spark)...resulting in a cranking-no-start. As you are experiencing.
However, a cranking-no-start can be caused by many things. Most of which are not CPS related.
Diagnosing crank-no-start conditions typically starts with verifying:
1. Spark is present
2. Fuel delivery is good
3. Air delivery is good
Only if spark was not present would the CPS be considered as a culprit.
If you are having difficulty determining if the CPS is bad now, how was it determined that it was bad when you initial had the problem? In your original post it is simply stated as fact ("cps failed").
Was it tested with a scope, or was it just assumed to be bad? If it was not tested with a scope and known for a fact to be bad...your next step is to return to the basic diagnostic steps for a crank-no-start condition. Has that already been done? Is spark present?
You are correct that a CPS can be bad out of the box. And because PCMs are very picky about reading the CPS signals, sometimes aftermarket CPSs don't work well. But even more likely than all of that, is that if replacing the CPS didn't change anything...then the CPS is not the problem.
On a 3 wire CPS as you find in the Jeep, 2 wires are used to provide a power circuit to the sensor which is used to power a small electromagnet that produces changes when other metal comes near it. These changes are then communicated as voltage fluctuations on the 3rd wire (usually called the signal wire) to the PCM (engine computer).
What this means is that testing a CPS with a multimeter, despite the posts and videos that make it seem otherwise, is only testing that these wires are in good shape and are not damaged or otherwise failing within the sensor. So if there is a continuity problem with the wires, they can help demonstrate that the CPS is bad and needs to be replaced. So these tests can "rule-in" that the CPS is a problem. However, because these tests do not concern the signal quality being communicated to the PCM, they can not "rule-out" the CPS as being a problem.
The trouble being, that even after doing the meter test, the CPS could still be the problem. And the failure modes of CPS often are just like that, such that the wires are fine but because of the degradation of the sensor it is no longer providing a useful or recognized signal to the computer.
CPS signals are tested using a scope in order to see the pattern of the signal. Typically scope is set up to measure both the camshaft position sensor and the crankshaft position sensor, because not only must their signals be appropriate, they must be appropriate in relationship to each other. If any of these these things are not as they should be, the computer will not initiate ignition (spark)...resulting in a cranking-no-start. As you are experiencing.
However, a cranking-no-start can be caused by many things. Most of which are not CPS related.
Diagnosing crank-no-start conditions typically starts with verifying:
1. Spark is present
2. Fuel delivery is good
3. Air delivery is good
Only if spark was not present would the CPS be considered as a culprit.
If you are having difficulty determining if the CPS is bad now, how was it determined that it was bad when you initial had the problem? In your original post it is simply stated as fact ("cps failed").
Was it tested with a scope, or was it just assumed to be bad? If it was not tested with a scope and known for a fact to be bad...your next step is to return to the basic diagnostic steps for a crank-no-start condition. Has that already been done? Is spark present?
You are correct that a CPS can be bad out of the box. And because PCMs are very picky about reading the CPS signals, sometimes aftermarket CPSs don't work well. But even more likely than all of that, is that if replacing the CPS didn't change anything...then the CPS is not the problem.
02-05-2018, 11:05 PM
#5
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Year: 1999
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I've been trying to come up with a simple way to contribute to the questions here.
On a 3 wire CPS as you find in the Jeep, 2 wires are used to provide a power circuit to the sensor which is used to power a small electromagnet that produces changes when other metal comes near it. These changes are then communicated as voltage fluctuations on the 3rd wire (usually called the signal wire) to the PCM (engine computer).
What this means is that testing a CPS with a multimeter, despite the posts and videos that make it seem otherwise, is only testing that these wires are in good shape and are not damaged or otherwise failing within the sensor. So if there is a continuity problem with the wires, they can help demonstrate that the CPS is bad and needs to be replaced. So these tests can "rule-in" that the CPS is a problem. However, because these tests do not concern the signal quality being communicated to the PCM, they can not "rule-out" the CPS as being a problem.
The trouble being, that even after doing the meter test, the CPS could still be the problem. And the failure modes of CPS often are just like that, such that the wires are fine but because of the degradation of the sensor it is no longer providing a useful or recognized signal to the computer.
CPS signals are tested using a scope in order to see the pattern of the signal. Typically scope is set up to measure both the camshaft position sensor and the crankshaft position sensor, because not only must their signals be appropriate, they must be appropriate in relationship to each other. If any of these these things are not as they should be, the computer will not initiate ignition (spark)...resulting in a cranking-no-start. As you are experiencing.
However, a cranking-no-start can be caused by many things. Most of which are not CPS related.
Diagnosing crank-no-start conditions typically starts with verifying:
1. Spark is present
2. Fuel delivery is good
3. Air delivery is good
Only if spark was not present would the CPS be considered as a culprit.
If you are having difficulty determining if the CPS is bad now, how was it determined that it was bad when you initial had the problem? In your original post it is simply stated as fact ("cps failed").
Was it tested with a scope, or was it just assumed to be bad? If it was not tested with a scope and known for a fact to be bad...your next step is to return to the basic diagnostic steps for a crank-no-start condition. Has that already been done? Is spark present?
You are correct that a CPS can be bad out of the box. And because PCMs are very picky about reading the CPS signals, sometimes aftermarket CPSs don't work well. But even more likely than all of that, is that if replacing the CPS didn't change anything...then the CPS is not the problem.
On a 3 wire CPS as you find in the Jeep, 2 wires are used to provide a power circuit to the sensor which is used to power a small electromagnet that produces changes when other metal comes near it. These changes are then communicated as voltage fluctuations on the 3rd wire (usually called the signal wire) to the PCM (engine computer).
What this means is that testing a CPS with a multimeter, despite the posts and videos that make it seem otherwise, is only testing that these wires are in good shape and are not damaged or otherwise failing within the sensor. So if there is a continuity problem with the wires, they can help demonstrate that the CPS is bad and needs to be replaced. So these tests can "rule-in" that the CPS is a problem. However, because these tests do not concern the signal quality being communicated to the PCM, they can not "rule-out" the CPS as being a problem.
The trouble being, that even after doing the meter test, the CPS could still be the problem. And the failure modes of CPS often are just like that, such that the wires are fine but because of the degradation of the sensor it is no longer providing a useful or recognized signal to the computer.
CPS signals are tested using a scope in order to see the pattern of the signal. Typically scope is set up to measure both the camshaft position sensor and the crankshaft position sensor, because not only must their signals be appropriate, they must be appropriate in relationship to each other. If any of these these things are not as they should be, the computer will not initiate ignition (spark)...resulting in a cranking-no-start. As you are experiencing.
However, a cranking-no-start can be caused by many things. Most of which are not CPS related.
Diagnosing crank-no-start conditions typically starts with verifying:
1. Spark is present
2. Fuel delivery is good
3. Air delivery is good
Only if spark was not present would the CPS be considered as a culprit.
If you are having difficulty determining if the CPS is bad now, how was it determined that it was bad when you initial had the problem? In your original post it is simply stated as fact ("cps failed").
Was it tested with a scope, or was it just assumed to be bad? If it was not tested with a scope and known for a fact to be bad...your next step is to return to the basic diagnostic steps for a crank-no-start condition. Has that already been done? Is spark present?
You are correct that a CPS can be bad out of the box. And because PCMs are very picky about reading the CPS signals, sometimes aftermarket CPSs don't work well. But even more likely than all of that, is that if replacing the CPS didn't change anything...then the CPS is not the problem.
however, the new cps is also providing no spark, hence why I'm wondering if the new sensor is bad out of the box, I'm still searching for answers. Not sure if this is relevant, but the auxiliary fan goes at full speed when the key is put in the on position
02-06-2018, 10:28 AM
#6
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I agree with Jordan that your CPS is probably NOT your problem.
If your aux fan goes on when the key is in the ON position, you should check/test your CTS (Coolant Temp Sensor) that's located on the thermostat housing.
I would check all your ground wiring, check your CTS wiring, test the CTS yourself. I think you'll find that either the wiring or sensor is bad. That may or may not be your root problem. I'm not sure if the CTS can prevent spark if it's bad on an XJ, but it definitely can on other vehicles.
If your aux fan goes on when the key is in the ON position, you should check/test your CTS (Coolant Temp Sensor) that's located on the thermostat housing.
I would check all your ground wiring, check your CTS wiring, test the CTS yourself. I think you'll find that either the wiring or sensor is bad. That may or may not be your root problem. I'm not sure if the CTS can prevent spark if it's bad on an XJ, but it definitely can on other vehicles.
02-06-2018, 12:20 PM
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There are two reasons you may not get a spark, one is the CPS and the other is the cam sensor, or ignition pickup. I had to replace both to get the spark back.
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02-09-2018, 01:54 PM
#8
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Thanks everyone for all the info and help, I'm still diagnosing the issue using what info I've been given, I don't want to replace every sensor so am trying to track it down before I start dumping money into sensors. I can't find anywhere that says the Coolant Temp Sensor will prevent start. Swapped the relays around and that did not help either. To recap, the symptoms still are:
Jeep died when driving home a while ago and hasn't started since
Electric fan runs when the key is turned to on, AC is off obviously
No Spark- was tested for properly (Brand New CPS, not oem, could be defective)
No CEL, When CPS is plugged in gauges don't work, when it's unplugged they still don't
Engine Cranks and cranks and cranks but won't start
Has Fuel
The next step in my mind is to get an OEM CPS but that doesn't explain the Electric fan issue, or replace the CTS (will it cause a no start??)
Jeep died when driving home a while ago and hasn't started since
Electric fan runs when the key is turned to on, AC is off obviously
No Spark- was tested for properly (Brand New CPS, not oem, could be defective)
No CEL, When CPS is plugged in gauges don't work, when it's unplugged they still don't
Engine Cranks and cranks and cranks but won't start
Has Fuel
The next step in my mind is to get an OEM CPS but that doesn't explain the Electric fan issue, or replace the CTS (will it cause a no start??)
02-09-2018, 04:15 PM
#9
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Year: 1999
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UPDATE: SHE STARTED!!!!....but was sputtering/threatening to stall well, almost stalled a couple times so I kept my foot on the gas to keep the revs above 1000, gave it a bit more gas and it started to backfire around 2600-2700 rpm. Shut her down after 10 ish minutes and now no start once again, won't even turn over...I'm lost
02-09-2018, 07:39 PM
#11
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Waiting on a buddy to borrow his code reader and fuel pressure gauge...the cel is now gone, efan was on due to a blown fuse, replaced the fuse and the fan shut off (was fuse F22 in the pdc). I'm now suspecting this issue is more electrical related than CPS or Fuel but am totally lost on what to do no.
02-09-2018, 09:42 PM
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With all things electrical, you first must check/clean/tighten all your grounds. Do this first because it's easy and costs you nothing but a few minutes of your time.
With your description of the behavior, I'd also make 100% sure your battery cables are clean and tight.
I'd consider load testing your battery as well just to be sure it's good. I don't know if that's as easy to do on your side of the border as it is here, but here it's a free test that Autozone or other retailers can do on or off the vehicle.
In other words, eliminate all the simple stuff just to be sure it's not a cause or contributor to your issues.
Codes and fuel psi info is key to moving on with diagnostics, so maybe entice your buddy with beers or somethings to expedite helping,
With your description of the behavior, I'd also make 100% sure your battery cables are clean and tight.
I'd consider load testing your battery as well just to be sure it's good. I don't know if that's as easy to do on your side of the border as it is here, but here it's a free test that Autozone or other retailers can do on or off the vehicle.
In other words, eliminate all the simple stuff just to be sure it's not a cause or contributor to your issues.
Codes and fuel psi info is key to moving on with diagnostics, so maybe entice your buddy with beers or somethings to expedite helping,
02-10-2018, 06:46 AM
#13
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Just had the same thing happen to my MJ. It took 4 different CPS (Mopar, BWD, Wells, Echlin) to find one that worked. Some are just cheap made junk. I know, it is frustrating but ALWAYS get lifetime warranty if possible that way they have to exchange it. I now have 1 in my MJ and three working spares because of it.
02-10-2018, 12:24 PM
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With all things electrical, you first must check/clean/tighten all your grounds. Do this first because it's easy and costs you nothing but a few minutes of your time.
With your description of the behavior, I'd also make 100% sure your battery cables are clean and tight.
I'd consider load testing your battery as well just to be sure it's good. I don't know if that's as easy to do on your side of the border as it is here, but here it's a free test that Autozone or other retailers can do on or off the vehicle.
In other words, eliminate all the simple stuff just to be sure it's not a cause or contributor to your issues.
Codes and fuel psi info is key to moving on with diagnostics, so maybe entice your buddy with beers or somethings to expedite helping,
With your description of the behavior, I'd also make 100% sure your battery cables are clean and tight.
I'd consider load testing your battery as well just to be sure it's good. I don't know if that's as easy to do on your side of the border as it is here, but here it's a free test that Autozone or other retailers can do on or off the vehicle.
In other words, eliminate all the simple stuff just to be sure it's not a cause or contributor to your issues.
Codes and fuel psi info is key to moving on with diagnostics, so maybe entice your buddy with beers or somethings to expedite helping,
Today's game plan is to check (clean & tighten) every ground, as well as check all wiring and fuses even more thoroughly than I already have. Battery has been load tested and it's not great but still is fine. Hoping I can pull the code today even though the cel is no longer on and maybe that will lead me in the right direction.
02-10-2018, 12:29 PM
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Just had the same thing happen to my MJ. It took 4 different CPS (Mopar, BWD, Wells, Echlin) to find one that worked. Some are just cheap made junk. I know, it is frustrating but ALWAYS get lifetime warranty if possible that way they have to exchange it. I now have 1 in my MJ and three working spares because of it.