Bluto
New Member
I was told there are some sensores that only draw 5 volts. Does any one know which ones?
5V sensors
- Thread starter Bluto
- Start date
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projectSHO89
SHOless In St L
Note: I edited the first portion of this post to delete information which was not correct. My apologies if you relied on it. Corrected info is as follows.
Yes, a number of the sensors do use 5 V as the reference. I checked the TPS and the MAP sensor on mine to be 5V reference. According to the 89 EVTM, the following should also be on the 5 V reference: Shorting plug, EGR sensor, ACT sensor, knock sensor, ECT, PS pressure switch, and clutch switch in addition to the TPS and MAP sensors. It appears that the 5 V reference voltage is provided by a regulator internal to the ECA/PCM.
The HEGOs use 12 volts for the heater circuit but do not use a reference voltage. The output is rather low, in a range from .8 to 1.0 volts. Here's a tech tip on what the output of a HEGO should look like and how to test one: http://www.interro.com/techoxy.html
Steve
<small>[ October 01, 2002, 09:58 AM: Message edited by: projectSHO89 ]</small>
Yes, a number of the sensors do use 5 V as the reference. I checked the TPS and the MAP sensor on mine to be 5V reference. According to the 89 EVTM, the following should also be on the 5 V reference: Shorting plug, EGR sensor, ACT sensor, knock sensor, ECT, PS pressure switch, and clutch switch in addition to the TPS and MAP sensors. It appears that the 5 V reference voltage is provided by a regulator internal to the ECA/PCM.
The HEGOs use 12 volts for the heater circuit but do not use a reference voltage. The output is rather low, in a range from .8 to 1.0 volts. Here's a tech tip on what the output of a HEGO should look like and how to test one: http://www.interro.com/techoxy.html
Steve
<small>[ October 01, 2002, 09:58 AM: Message edited by: projectSHO89 ]</small>
Bluto
New Member
Thanks
I think i will just replace every sensor.
Maybe then I can get some codes out of the car.
I don't know if I mentioned it before but I was told a 5v sensor is causing my computer to lock up(as far as giving codes).
Thanks again
-Bluto
I think i will just replace every sensor.
Maybe then I can get some codes out of the car.
I don't know if I mentioned it before but I was told a 5v sensor is causing my computer to lock up(as far as giving codes).
Thanks again
-Bluto
projectSHO89
SHOless In St L
Phooey!
If the computer were "locked up", the engine would never run. Just think "blue screen of death".
Start over.
Does the CEL illuminate when you start the engine?
Does it go out after the engine starts or does it stay on?
If it stays on all the time, turn engine and ignition to off and measure the resistance from the STO pin of the self test connector to ground. If it shows a short, either you have a wiring fault or the output driver in the ECA shorted to ground. A short to ground n this line will result in an always-on CEL and no codes output. If your CEL is always on, I'd bet on one of these.
Steve
If the computer were "locked up", the engine would never run. Just think "blue screen of death".
Start over.
Does the CEL illuminate when you start the engine?
Does it go out after the engine starts or does it stay on?
If it stays on all the time, turn engine and ignition to off and measure the resistance from the STO pin of the self test connector to ground. If it shows a short, either you have a wiring fault or the output driver in the ECA shorted to ground. A short to ground n this line will result in an always-on CEL and no codes output. If your CEL is always on, I'd bet on one of these.
Steve
Bluto
New Member
Thanks Steve,
It seems to be something else.
The CE light operates properly, and I can't get KOEO codes.
Any other ideas?
It seems to be something else.
The CE light operates properly, and I can't get KOEO codes.
Any other ideas?
projectSHO89
SHOless In St L
Verify that the ground (Signal Return) pin on the self test plug is grounded to chassis ground.
Verify continuity of the STI (Self Test Input) wire to ECA pin 48.
If these continuit checks show that the lines are good, you have a fault in the ECA.
Steve
Verify continuity of the STI (Self Test Input) wire to ECA pin 48.
If these continuit checks show that the lines are good, you have a fault in the ECA.
Steve
rangerj
Active Member
Bluto,
It has been my experience that a sensor that is expected, by the computer, to draw UP TO 5 volts, will not "code" as long as the sensor is drawing 5 volts, or less.
However, a sensor that is drawing close to 5 volts is very likely to be on its way to failing, and may be causing intermitent problems.
Many of the sensors can be tested for the amount of ohms, (resistance) and determined to be good or bad, depending on the test results.
Would someone please post the resistance peramiters, and other test proceedures, for the various sensors?
I have also found that very frequently the problem is a poor electrical connection, often due to corrosion. I recently spent about 20 hours cleaning connections and coating the connectors with Kopr-shield.
Kopr-shield is like anti-sieze compound, but is copper in color. It is available from Eastwoods, and may be available from a local auto parts stores. It is specifically made for electrical connections. A small bottle is about $8 plus shipping.
There are also some greases made to keep electrical connections clean and promote conductivity. Would someone please post the brand names of these, and where to get them.
Lastly, check ALL of your GROUND connections. Make sure they are clean and making good contact. Hope this helps, rangerj
It has been my experience that a sensor that is expected, by the computer, to draw UP TO 5 volts, will not "code" as long as the sensor is drawing 5 volts, or less.
However, a sensor that is drawing close to 5 volts is very likely to be on its way to failing, and may be causing intermitent problems.
Many of the sensors can be tested for the amount of ohms, (resistance) and determined to be good or bad, depending on the test results.
Would someone please post the resistance peramiters, and other test proceedures, for the various sensors?
I have also found that very frequently the problem is a poor electrical connection, often due to corrosion. I recently spent about 20 hours cleaning connections and coating the connectors with Kopr-shield.
Kopr-shield is like anti-sieze compound, but is copper in color. It is available from Eastwoods, and may be available from a local auto parts stores. It is specifically made for electrical connections. A small bottle is about $8 plus shipping.
There are also some greases made to keep electrical connections clean and promote conductivity. Would someone please post the brand names of these, and where to get them.
Lastly, check ALL of your GROUND connections. Make sure they are clean and making good contact. Hope this helps, rangerj
projectSHO89
SHOless In St L
Actually, sensors and such components don't 'draw' 5 volts.
5 volts is the reference voltage supplied to them, the sensor will draw a few milliamps of CURRENT, but not voltage. The ouput of an analog sensor will be some value between ground and the reference voltage.
A defective (ie, shorted) sensor may attempt to draw too much current. This can load the DC supply down to the point that it is putting out a reduced voltage at a heavy current. FWIW, resistive sensors (and resistors in general)rarely short. In 26 years of electronics service, I've only run across one shorted resistor (happened to be a wire-wound resistor). Normal failure mode for these devices is to either open up, go non-linear, or to become intermittent due to an internal mechanical fault.
Corrosion in the connectors falls under the general category of "mechanical" fault, since the mechanical contact necessary for conduction has failed. Cleaning the connectors and using a product like Kopr-shield is a very good idea...
Steve
89
5 volts is the reference voltage supplied to them, the sensor will draw a few milliamps of CURRENT, but not voltage. The ouput of an analog sensor will be some value between ground and the reference voltage.
A defective (ie, shorted) sensor may attempt to draw too much current. This can load the DC supply down to the point that it is putting out a reduced voltage at a heavy current. FWIW, resistive sensors (and resistors in general)rarely short. In 26 years of electronics service, I've only run across one shorted resistor (happened to be a wire-wound resistor). Normal failure mode for these devices is to either open up, go non-linear, or to become intermittent due to an internal mechanical fault.
Corrosion in the connectors falls under the general category of "mechanical" fault, since the mechanical contact necessary for conduction has failed. Cleaning the connectors and using a product like Kopr-shield is a very good idea...
Steve
89
Bluto
New Member
I will go from there.
I hope to report back by the weekend.
Thanks
Bluto
I hope to report back by the weekend.
Thanks
Bluto
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