M272 Crankshaft position sensor voltage
05-09-2018, 04:57 PM
#1
Junior Member
Thread Starter
M272 Crankshaft position sensor voltage
Hi Guys ,
I'm working on a 2006 c230 coupe with a m272 v6 motor.
Its giving me a crankshaft position fault . Fault is described as follows
Motor Control:
Motor Electronics (MB: 0024467340)
Fault: Position sensor 1 for the crankshaft has an electrical fault. Code: 000703
I've attached the Diagnostics report just incase Ive missed something.
My problem is that from the cranshaft, I have 3 wires the be giving me Earth, 5Volts (signal) & 12volts Constant)
instead I'm getting earth, 5Volts and 5Volts. Is my assumption correct or is the latter correct ?
I supplied 12Volts directly from the battery and the car started and idled for 20mins then cut off .
I'm working on a 2006 c230 coupe with a m272 v6 motor.
Its giving me a crankshaft position fault . Fault is described as follows
Motor Control:
Motor Electronics (MB: 0024467340)
Fault: Position sensor 1 for the crankshaft has an electrical fault. Code: 000703
I've attached the Diagnostics report just incase Ive missed something.
My problem is that from the cranshaft, I have 3 wires the be giving me Earth, 5Volts (signal) & 12volts Constant)
instead I'm getting earth, 5Volts and 5Volts. Is my assumption correct or is the latter correct ?
I supplied 12Volts directly from the battery and the car started and idled for 20mins then cut off .
05-09-2018, 08:26 PM
#2
Super Member
It's a good thing that you put your location in your profile. Otherwise, I'd be giving you a "ton of ******" (ranting/complaining :-) about reading "Earth" instead of "Ground".
But, this is a great question for someone like me - Mech/Elec/Computer Geek.
Still, I'm lazy, so I'll first list the following links:
https://www.picoauto.com/library/aut...ctive-running/
https://www.1aauto.com/content/artic...sensor-testing
Basically, the output of the CPS is a series of small pluses, that have some percentage relationship to the engine RPMs and the crank-position.
A leading pulse, or a longer pulse, or some other indicator, indicates that the crank is in position "X" (often TDC - Cyl 1 Top Dead Center).
Without a "scope", you can not really see the output of the CPS.
A DMV (meter) may show some small voltages on the "AC" setting. But, BFD (Big "frigging" Deal)! That does not indicate that the pulses are of good shape, size, voltage, etc. And, different DMVs and different CPS devices may not show anything even with a good CPS and wiring.
Imho, replace the CPS with a MB OEM part.
Cheap CPS units are KNOWN to fail quickly and to not be reliable.
Good Luck!
But, this is a great question for someone like me - Mech/Elec/Computer Geek.
Still, I'm lazy, so I'll first list the following links:
https://www.picoauto.com/library/aut...ctive-running/
https://www.1aauto.com/content/artic...sensor-testing
Basically, the output of the CPS is a series of small pluses, that have some percentage relationship to the engine RPMs and the crank-position.
A leading pulse, or a longer pulse, or some other indicator, indicates that the crank is in position "X" (often TDC - Cyl 1 Top Dead Center).
Without a "scope", you can not really see the output of the CPS.
A DMV (meter) may show some small voltages on the "AC" setting. But, BFD (Big "frigging" Deal)! That does not indicate that the pulses are of good shape, size, voltage, etc. And, different DMVs and different CPS devices may not show anything even with a good CPS and wiring.
Imho, replace the CPS with a MB OEM part.
Cheap CPS units are KNOWN to fail quickly and to not be reliable.
Good Luck!
Last edited by RedGray; 05-09-2018 at 08:31 PM.
05-09-2018, 11:02 PM
#3
Junior Member
Thread Starter
@Redgray .
Thank you for the reply .
my question was around the values I should be getting before cranking the engine.
i.e: when the ignition is turn on and ready to start .
Tomorrow I'll replace the crank sensor worth another one coming from a running car. In fact I'll test and see if I'm getting the same values.
thank you very much for the attached sites . I'll be going through them as well. I also attached a diagnostics report .it's not from a star machine but it's pretty accurate . If could please go through it maybe there might be something there that I missed .
Thank you for the reply .
my question was around the values I should be getting before cranking the engine.
i.e: when the ignition is turn on and ready to start .
Tomorrow I'll replace the crank sensor worth another one coming from a running car. In fact I'll test and see if I'm getting the same values.
thank you very much for the attached sites . I'll be going through them as well. I also attached a diagnostics report .it's not from a star machine but it's pretty accurate . If could please go through it maybe there might be something there that I missed .
05-09-2018, 11:14 PM
#4
Super Member
The value of the sensor output without the engine turning isn't important.
Note that the engine does not have to run, to see the output of the CPS. The output of the CPS is valid and correct when the engine is cranking/turning-over.
Otherwise, there's no way that the engine computer would know when to pulse the injectors, or to fire the spark plugs.
Good Luck!
Note that the engine does not have to run, to see the output of the CPS. The output of the CPS is valid and correct when the engine is cranking/turning-over.
Otherwise, there's no way that the engine computer would know when to pulse the injectors, or to fire the spark plugs.
Good Luck!
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leeroytandy (05-11-2018)
05-09-2018, 11:34 PM
#5
Super Member
Btw, the CPS sensor works by detecting a changing "magnetic field".
The notches on the ring on the crankshaft produce a weak magnetic area. Or, you could say that the "points" on the ring on the crankshaft produce a "strong" magnetic area.
The CPS sensor detects those changing "magnetic areas" (notches), and the CPS produces positive and negative voltages as the magnetic field increases then collapses.
So, if the engine is not turning, then the output of the sensor will depend on the design of the sensor and the engine computer. And, that could change with different versions of the sensor or engine computer.
That's a very rough simplified version of what the CPS does, and how it works.
It's more involved. But, imho, only interesting to people (like me) that like the more in depth details of how magnetic fields work/interact.
I think that it's neat how there can be a non-contact position sensor that works in a harsh environment like an engine, or with the ABS wheel sensors.
In general, there's no real value or concern about what the voltage is of the CPS sensor when the ignition is on, but the engine is not turning over.
Who cares? :-)
I hope the above description helps in the understanding a little. *I* find it interesting. But, this is the type of stuff that I do. :-)
The notches on the ring on the crankshaft produce a weak magnetic area. Or, you could say that the "points" on the ring on the crankshaft produce a "strong" magnetic area.
The CPS sensor detects those changing "magnetic areas" (notches), and the CPS produces positive and negative voltages as the magnetic field increases then collapses.
So, if the engine is not turning, then the output of the sensor will depend on the design of the sensor and the engine computer. And, that could change with different versions of the sensor or engine computer.
That's a very rough simplified version of what the CPS does, and how it works.
It's more involved. But, imho, only interesting to people (like me
) that like the more in depth details of how magnetic fields work/interact.I think that it's neat how there can be a non-contact position sensor that works in a harsh environment like an engine, or with the ABS wheel sensors.
In general, there's no real value or concern about what the voltage is of the CPS sensor when the ignition is on, but the engine is not turning over.
Who cares? :-)
I hope the above description helps in the understanding a little. *I* find it interesting. But, this is the type of stuff that I do. :-)
05-11-2018, 01:29 AM
#6
Junior Member
Thread Starter
The value of the sensor output without the engine turning isn't important.
Note that the engine does not have to run, to see the output of the CPS. The output of the CPS is valid and correct when the engine is cranking/turning-over.
Otherwise, there's no way that the engine computer would know when to pulse the injectors, or to fire the spark plugs.
Good Luck!
Note that the engine does not have to run, to see the output of the CPS. The output of the CPS is valid and correct when the engine is cranking/turning-over.
Otherwise, there's no way that the engine computer would know when to pulse the injectors, or to fire the spark plugs.
Good Luck!
05-11-2018, 02:53 AM
#7
Super Member
In general, sensors get regulated 5 volts DC.
The "exception" is the MAF. But, that's not really an exception. The MAF has it's own electronics on the unit. So, it's not really "12volts" going to the "MAF Sensor", it's really 12V going to the "MAF Assembly".
For sensors that send information back to the computer, it wouldn't make sense to use "12v" to the sensors.
That's because "12v/battery-voltage" varies from 11.5v to 14.5v. So, the "standard" is to use regulated 5V. However, that does not prevent a manufacture from doing what they want. However, a lot of sensors are now bought from specialty companies - like Bosh. So, that's even more of an incentive to do things the "standard way".
Still, some companies like GM like to design their own "fail proof" Crank Sensors. It's actually two independent sensors in one housing. That way, one one sensor fails, an error is shown, and the owner can get the sensor-unit replaced while the secondary sensor is used.
Note, that's in theory!!
In real-life, the GM sensors are some of the biggest POS and most unreliable cr*p sensors ever made. They almost never ever ever ever ever ever do what the theory says. Maybe one GM Dealer mechanic saw it happen once. But, I've never read or seen those POS GM crank sensors "fail gracefully".
So.., the point is, companies can be clueless and stupid like GM and design their own sensors, or they can go to the experts, like Bosh, and get a sensor that works better, is more reliable, and cheaper.
An exception to the buy the sensor from a specificity company is the ..... MAF! Or, more correctly, the MAF assembly. Here, to be fair, for a long time, GM's designs and patents made most of the other MAFs look like jokes.
Fwiw, back in the "old days", when we had non computer-controlled engines, then 12v/battery-voltage would go to a sensor like the temperature sensor. And, "something" would show up on the temperature gauge. The readings weren't accurate at all. But, it really didn't matter if the reading was off by ~5 degrees. And, most gauges just had "zones" for cold/good/hot.
To get more accurate temperature readings from 12v gauges, the gauge itself would have battery voltage going into some electronics. That way, the gauge could correct for the varying voltage that would come from the sensor, as the battery voltage varied. However, since there are voltage and ground differences between the sensor and the gauge, even those gauges are only "so so accurate" in real life.
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05-11-2018, 03:02 AM
#8
Super Member
In general, sensors get regulated 5 volts DC.
So.., the point is, companies can be clueless and stupid like GM and design their own sensors, or they can go to the experts, like Bosh, and get a sensor that works better, is more reliable, and cheaper.
So.., the point is, companies can be clueless and stupid like GM and design their own sensors, or they can go to the experts, like Bosh, and get a sensor that works better, is more reliable, and cheaper.
From:
https://www.autozone.com/repairinfo/...00c1528006ab60
======
Unplug the Crankshaft Position Sensor (CKPS) connector.
Turn the ignition ON .
Using a voltmeter, measure the voltage from the wiring harness connector 8-volt supply circuit (orange wire) to ground. Refer to the accompanying wiring illustration.
If the voltage is 8-9.5 volts, skip to the next step.
If the voltage measured is lower than 8 volts, or higher than 9.5 volts, the CKPS is not receiving the correct current to function properly. There is a problem in the wiring or related components.
======
Btw, see:
https://www.samarins.com/glossary/crank_sensor.html
https://www.samarins.com/glossary/crank_sensor2.html
For the Hall-type sensors, the reference voltage (typically +5V) and the ground signal must be tested. The most accurate way to test a crankshaft position sensor is checking the sensor signal with an oscilloscope.
Also: From the company I love to "leg-hump":
https://www.pelicanparts.com/techart...or_Testing.htm
Good Luck!
