Stays in Open loop, fans run constantly
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Instructor
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Stays in Open loop, fans run constantly
Tell me if this makes sense
Ran DM on the vette (90, vert, AT) because I failed smog due to egr not operating. Guy mentions at the time that the fans are running constantly so it might never be going to closed loop.
Anyway, it is definitely staying in open loop and DM shows the engine temp as being 123.5C. I know for a fact this ain't right because you can put your hand on the radiator hose and it's just not that hot. The inside gauge (NOT that I put a lot of faith in it) shows the temp as barely getting warm.
Checked the sensor and the wire is connected but I'm thinking the sensor is possibly bad so the ECM is telling the fans to run constantly because it thinks the engine is at 250+ degrees F.
Still doesn't explain the ECM sticking in Open Loop though (or at least to my understanding).
Does anyone know off the top of their head what the resistance should be for the temp sensor?
If it's good am I possibly looking at ECM issues?
Ran DM on the vette (90, vert, AT) because I failed smog due to egr not operating. Guy mentions at the time that the fans are running constantly so it might never be going to closed loop.
Anyway, it is definitely staying in open loop and DM shows the engine temp as being 123.5C. I know for a fact this ain't right because you can put your hand on the radiator hose and it's just not that hot. The inside gauge (NOT that I put a lot of faith in it) shows the temp as barely getting warm.
Checked the sensor and the wire is connected but I'm thinking the sensor is possibly bad so the ECM is telling the fans to run constantly because it thinks the engine is at 250+ degrees F.
Still doesn't explain the ECM sticking in Open Loop though (or at least to my understanding).
Does anyone know off the top of their head what the resistance should be for the temp sensor?
If it's good am I possibly looking at ECM issues?
Le Mans Master
Joined: Aug 2000
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From: Australia
Anyway, it is definitely staying in open loop and DM shows the engine temp as being 123.5C
I'm thinking the sensor is possibly bad so the ECM is telling the fans to run constantly because it thinks the engine is at 250+ degrees F.
Still doesn't explain the ECM sticking in Open Loop though (or at least to my understanding).
I'm thinking the sensor is possibly bad so the ECM is telling the fans to run constantly because it thinks the engine is at 250+ degrees F.
Still doesn't explain the ECM sticking in Open Loop though (or at least to my understanding).
If ECM does not see the O2 V cycle Hi-Lo-Hi it won't engage CL
For $12 -$14 hardly worth the trouble of testing ;
just put a new one in and consider it periodic maintainance ( every 20 years )
Last edited by rodj; May 20, 2012 at 07:45 PM.
Safety Car
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From: VA
123.5 C would be about 255 F, which says to me that there is an open or short circuit, which should result in a thrown code, fans turned on, and staying in open loop.
Thread Starter
Instructor
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What are your O2 values on DM?
If ECM does not see the O2 V cycle Hi-Lo-Hi it won't engage CL
http://www.thirdgen.org/techboard/po...095-post3.html
trying to add screen cap but it's not taking the link... odd...Must just be my day to **** off computers...
For $12 -$14 hardly worth the trouble of testing ;
just put a new one in and consider it periodic maintainance ( every 20 years )
If ECM does not see the O2 V cycle Hi-Lo-Hi it won't engage CL
http://www.thirdgen.org/techboard/po...095-post3.html
trying to add screen cap but it's not taking the link... odd...Must just be my day to **** off computers...
For $12 -$14 hardly worth the trouble of testing ;
just put a new one in and consider it periodic maintainance ( every 20 years )
And agreed re: testing the sensor. More effort than it's worth.
The DTC error is an EST monitor error which I've read to be the result of when I set the timing (which I did) and didn't reset it.
Good point. This is after replacing the intake... maybe I trashed something. Thanks to both of you for the ideas.
Last edited by Baller; May 20, 2012 at 09:50 PM. Reason: add screen cap
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
The high temperature is a result of low resistance in the circuit, either bad sensor or wiring shorted to ground. Unplug the CTS to see how that affects things -- it will isolate the problem to the sensor or wiring.
The ECM temperature sensor and the sensor for the dash gauge are essentially the same (they both have the same response curves), just in different packages.
If the O2 sensor never goes over approximately .5 volts the ECM will assume it isn't hot enough and will not go into closed loop mode.
The ECM temperature sensor and the sensor for the dash gauge are essentially the same (they both have the same response curves), just in different packages.
If the O2 sensor never goes over approximately .5 volts the ECM will assume it isn't hot enough and will not go into closed loop mode.
Thread Starter
Instructor
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Checked the CTS and when the car is cool it only has 104 ohms which according the the 3rd gen chart someone posted would make the coolant temp around 235 F which I know there is no way. The reading should have been something like 350 ohms.
Checked the wires to into and the yellow shows open and the black is grounded.
Checked the wires to into and the yellow shows open and the black is grounded.
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
What I meant is that if you unplug the sensor you should see a very low temperature on a scan tool. The open circuit is a very high resistance. Obviously this will also affect how your car runs.
Just for reference, this is the CTS chart from my '86 FSM (I think it's interesting that the C & F curves intersect at -40 degrees -- learned this 20 years ago on a former job):
Just for reference, this is the CTS chart from my '86 FSM (I think it's interesting that the C & F curves intersect at -40 degrees -- learned this 20 years ago on a former job):
Last edited by Cliff Harris; May 27, 2012 at 11:30 PM.
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Thread Starter
Instructor
Joined: Oct 2010
Posts: 140
Likes: 0
What I meant is that if you unplug the sensor you should see a very low temperature on a scan tool. The open circuit is a very high resistance. Obviously this will also affect how your car runs.
Just for reference, this is the CTS chart from my '86 FSM (I think it's interesting that the C & F curves intersect at -40 degrees -- learned this 20 years ago on a former job):
Just for reference, this is the CTS chart from my '86 FSM (I think it's interesting that the C & F curves intersect at -40 degrees -- learned this 20 years ago on a former job):
