Unplug CPS
09-29-2013, 01:05 PM
#1
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Unplug CPS
'89 Cherokee with a 16 month old Crankshaft Position Sensor. Today she wouldn't start, no spark off the ignition coil. Checked the ohms out on the nearly new CPS, looked good. I was about to go get a new coil & Ignition Control Module when my Dad found this youtube:
I unplugged the CPS, waited for 5 minutes just like the video instructs... she fired right up.
What is going on?
Should I replace the ICM? '89 Renix doesn't throw codes so I'm not sure if my ECU or ICM is ready to go out. Grounds are good on all my sensors, though, I'm still going to redo them via a write-up that is on the forum.
Any feedback is appreciated...
I unplugged the CPS, waited for 5 minutes just like the video instructs... she fired right up.
What is going on?
Should I replace the ICM? '89 Renix doesn't throw codes so I'm not sure if my ECU or ICM is ready to go out. Grounds are good on all my sensors, though, I'm still going to redo them via a write-up that is on the forum.Any feedback is appreciated...
09-29-2013, 01:17 PM
#2
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Year: 1998 Sport
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Possibly a bad CPS. If it worked after unplugging it and replugging it back in. Do your self a favor and replace it with a OEM one. After market one have a limited life span if they work at all. Also testing them isn't always 100% accurate. I had mine test good and I replaced it and it took care of my problems with it.
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BloNdeChiNeEz (04-08-2024)
09-29-2013, 01:33 PM
#4
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The CPS is a Hall sensor that generates a very specific voltage signal, interpreted by the ECU and forwarded on to the ICM to generate spark. There are several things that can affect the voltage signal to the ECU... debris on the sensor. It's magnetic and tends to collect powdered metal from within the bell housing although, I must admit, I've never heard of this actually causing a problem. The corrosion on the connector is another source of resistance that can alter the voltage seen by the ECU and is likely why unplugging and replugging may seem to solve the problem but in reality, it rarely does and is just a temporary remedy.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
09-29-2013, 01:34 PM
#5
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They really arn't that hard to change out. If you do it from the bottom. Make shure you have at least 2 or 3 feet of socket extensions and a swivel and you should have it out without much trouble. Give yourself about an hour for the job.
09-29-2013, 01:50 PM
#6
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The CPS is a Hall sensor that generates a very specific voltage signal, interpreted by the ECU and forwarded on to the ICM to generate spark. There are several things that can affect the voltage signal to the ECU... debris on the sensor. It's magnetic and tends to collect powdered metal from within the bell housing although, I must admit, I've never heard of this actually causing a problem. The corrosion on the connector is another source of resistance that can alter the voltage seen by the ECU and is likely why unplugging and replugging may seem to solve the problem but in reality, it rarely does and is just a temporary remedy.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
good to know about checking the AC voltage versus the resistance. Thanks!
09-29-2013, 01:55 PM
#7
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Thanks for all the input!!!
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09-30-2013, 05:19 PM
#8
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The CPS is a Hall sensor that generates a very specific voltage signal, interpreted by the ECU and forwarded on to the ICM to generate spark. There are several things that can affect the voltage signal to the ECU... debris on the sensor. It's magnetic and tends to collect powdered metal from within the bell housing although, I must admit, I've never heard of this actually causing a problem. The corrosion on the connector is another source of resistance that can alter the voltage seen by the ECU and is likely why unplugging and replugging may seem to solve the problem but in reality, it rarely does and is just a temporary remedy.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
Where did you get your CPS? Auto parts stores typically sell Chinese-made CPSs that aren't reliable. Many have experienced failure right out of the box. In order to test, find Cruiser54s Renix tips and check the actual voltage (AC, not DC) being produced by the CPS, not the resistance (Ohms). The voltage should be between 0.35 and 0.5 volts, AC. If it's below 0.35 volts then it needs to be replaced (again) and I would recommend an OEM CPS. They're more expensive but you get what you pay for and experience demonstrates that they are far more reliable than those from AutoZone or O'Reilly's.
The best advice I can give you regarding technique for replacing your CPS is to slide in feet-first from the driver's side. It seems overly simplistic but you'll be surprised how much easier and painless it is to get your hands and arms up in there.
3.5-3.9 volts AC at start up, dropping to about 2 volts at idle. Guess I'll get a new one. I can't remember which brand the CPS was, but it wasn't OEM. Live & learn.
Thanks again guys...
09-30-2013, 06:58 PM
#9
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Note the modification noted in the write-up below. If you want to see photos and also explre other cheap and easy fixes for your Jeep, click on the link in my signature. #7 specifically addresses the CPS.
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
09-30-2013, 07:26 PM
#10
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Year: 1989
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Note the modification noted in the write-up below. If you want to see photos and also explre other cheap and easy fixes for your Jeep, click on the link in my signature. #7 specifically addresses the CPS.
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8" from the stock 5/16", or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Revised 01-26-2013
I had planned on doing everything in your thread (starting at your 1st post), but I hadn't seen the CPS stuff yet.
That makes much more sense to use the hall voltage generation from the magnet with the connector disconnected for the test. I had stripped back a tiny bit of insulation on both legs to test the potential... I was wondering why my voltages were so different than what F1Addict posted. Figured he had misplaced a decimal point. I'll redo my test tonight.
Called my local Jeep to get a CPS ordered just to be safe, parts guy said they're on back order for a few weeks & it would be a few weeks after that before they some 'em at the dealer ship level. Does NAPA source OEM parts (saw NAPA in what you quoted from your write-up)? I would be pretty sad if I had to wait a month for the Jeep dealership to get one, planned on seeing some family this month & I was hoping to take my Dad out in the Jeep...
09-30-2013, 07:29 PM
#11
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Get one from Napa, their Premium line, and drill the upper hole.
09-30-2013, 07:31 PM
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09-30-2013, 08:28 PM
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