Intake Air Temperature High....
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Joined: Jul 2002
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From: Cape Coral FL
Intake Air Temperature High....
I had the diagnostic codes of C 25 and H 25 coming up and setting off the SYS warning in the dash. I checked and found that it was both a Current and History warning of a High Intake Air Temperature.
After doing some searches on this site, I found that the sensor can be checked for resistance depending on the air temperature. Mine was shorted with no resistance showing on a meter check, so I replaced the sensor.
Right after I replaced the sensor, I didn't have the C 25 diagnostic code anymore and thought it would just be a matter of time before the H 25 went away. However, all week it still showed the SYS warning, and today after checking the codes again, I am getting a C 25 and an H 25!
Can anyone suggest what I might check next?
Thanks.
Steve Nix
After doing some searches on this site, I found that the sensor can be checked for resistance depending on the air temperature. Mine was shorted with no resistance showing on a meter check, so I replaced the sensor.
Right after I replaced the sensor, I didn't have the C 25 diagnostic code anymore and thought it would just be a matter of time before the H 25 went away. However, all week it still showed the SYS warning, and today after checking the codes again, I am getting a C 25 and an H 25!
Can anyone suggest what I might check next?
Thanks.
Steve Nix
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Instructor
Joined: Jul 2002
Posts: 211
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From: Cape Coral FL
No I did not reset the codes, but the Current C 25 code did not show up right after I changed the sensor, but it is showing up again now, a week later.
I don't think it makes any difference, but I have a '93 LT 1.
I don't think it makes any difference, but I have a '93 LT 1.
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From: moraga ca
Sometimes on computer controlled cars, I will disconnect the battery for a few minutes and reconnect. This clears all codes and "reboots" the computer for a fresh start. Sometimes it will fix things.
Racer
Joined: Dec 2006
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From: shapleigh maine
Hey Steve is it SYS light or Service Engine Soon light? Code 25 for SYS light is for courtesy lamp relay control circuit, code 25 for ECM is IAT sensor. Possible you are diagnosing wrong computer? Let me know if you need CCM diagnostics.
Bob
Bob
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From: Cape Coral FL
The SYS warning comes on, then when I check for codes by shorting A & G, it shows "1" and then codes "C 25" and "H 25", so I'm not really sure?
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From: Cape Coral FL
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Thread Starter
Instructor
Joined: Jul 2002
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From: Cape Coral FL
Thread Starter
Instructor
Joined: Jul 2002
Posts: 211
Likes: 0
From: Cape Coral FL
OK, I disconnected the negative side of the battery and reconnected after about 30 seconds. Same SYS warning light comes on.
I also checked the passenger side courtesy light. It did NOT come on with the ignition on and passenger door open. I pulled down the panel, and the light (which sort of looks like a fuse, tested for continuity, it was not blown). Then I checked the fuse box on the passenger side, and checked both the left hand and right hand courtesy lights (in the same row as radio but on the other end) and both fuses were good.
Any other ideas?
Steve
I also checked the passenger side courtesy light. It did NOT come on with the ignition on and passenger door open. I pulled down the panel, and the light (which sort of looks like a fuse, tested for continuity, it was not blown). Then I checked the fuse box on the passenger side, and checked both the left hand and right hand courtesy lights (in the same row as radio but on the other end) and both fuses were good.
Any other ideas?
Steve
Last edited by SteveNix; Jul 2, 2011 at 04:39 PM.
Racer
Joined: Dec 2006
Posts: 499
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From: shapleigh maine
Steve A - G is CCM A -B is ECM
Try this
CIRCUIT DESCRIPTION
The courtesy lamp relay coil circuit is completed by the CCM when it receives a courtesy lamps "ON" request from any of a number of different inputs door locks, door ajar switches); the CCM grounds CKT 690, energizing the relay coil.
DTC 25 will set when CKT 690 is NOT at battery voltage for over 600 milliseconds while the CCM is NOT attempting to actuate the courtesy lamp relay not asking for courtesy lamps "ON").
I have some more info if you need it.
Bob
Try this
CIRCUIT DESCRIPTION
The courtesy lamp relay coil circuit is completed by the CCM when it receives a courtesy lamps "ON" request from any of a number of different inputs door locks, door ajar switches); the CCM grounds CKT 690, energizing the relay coil.
DTC 25 will set when CKT 690 is NOT at battery voltage for over 600 milliseconds while the CCM is NOT attempting to actuate the courtesy lamp relay not asking for courtesy lamps "ON").
I have some more info if you need it.
Bob
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From: Cape Coral FL
That's great Bob, thank you for finding that. My first question is, where do I find the "courtesy lamp relay" so I can do the first test?
Steve
Steve
Steve A - G is CCM A -B is ECM
Try this
CIRCUIT DESCRIPTION
The courtesy lamp relay coil circuit is completed by the CCM when it receives a courtesy lamps "ON" request from any of a number of different inputs door locks, door ajar switches); the CCM grounds CKT 690, energizing the relay coil.
DTC 25 will set when CKT 690 is NOT at battery voltage for over 600 milliseconds while the CCM is NOT attempting to actuate the courtesy lamp relay not asking for courtesy lamps "ON").
I have some more info if you need it.
Bob
Try this
CIRCUIT DESCRIPTION
The courtesy lamp relay coil circuit is completed by the CCM when it receives a courtesy lamps "ON" request from any of a number of different inputs door locks, door ajar switches); the CCM grounds CKT 690, energizing the relay coil.
DTC 25 will set when CKT 690 is NOT at battery voltage for over 600 milliseconds while the CCM is NOT attempting to actuate the courtesy lamp relay not asking for courtesy lamps "ON").
I have some more info if you need it.
Bob
Racer
Joined: Dec 2006
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From: shapleigh maine
I am going to hold you to that. I'll be in SW Florida at the end of August. Specifically in Nortrh Port. My folks live there. Going to check out Muscle Car City in PG. Any other suggestions? Seriously if you need any more help let me know.
Bob
Bob
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From: Cape Coral FL
