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Check engine light comes on when cooling fans are running. (1/4)
 6/29/16 1:51am
Tsmooth68
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Vette(s):
1993 Chevrolet Corvette Base Edition. Exterior Color is Polo Green with Tan interior. 5.7 LT-1 V-8 with 4-speed automatic transmission.


Joined: 6/4/2016
Posts: 13

Whenever the coolant fan is running on my 1993 C4, the check engine light comes on. The light eventually will turn off when the coolant fan is turned off. I scanned it and the codes were 44 & 64 (both codes reflect engine running to lean).
I replaced the oxygen sensor and the MAP sensor, and the light still come on. Could it be the coolant temperature sensor? I don't know. I am running out of options. If anyone has ran into this particular problem?


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Re: Check engine light comes on when cooling fans are running. (2/4)
 6/29/16 12:19pm
VegasVet
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las vegas, NV - USA

Vette(s):
Custom stalker kit, modified engine, new paint


Joined: 3/18/2014
Posts: 9

recently my Escalade had this problem found fuel pump pressure was low 47 instead of 53+ caused lean error

|UPDATED|6/29/2016 9:19:55 AM (AZT)|/UPDATED|


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Re: Check engine light comes on when cooling fans are running. (3/4)
 7/3/16 12:19pm
rtslt4
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Huntington Station, NY - USA

Vette(s):
1996 Black Cpe., Lt. Beige Int., LT4, 6 Spd., Corsa Exh., K & N, & Chrome Replc. Wheels.


Joined: 7/2/2013
Posts: 48

I never had this problem but based on the codes, I would check the fuel pressure as previously stated and check for vacuum leaks.

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Rts-LT4
Re: Check engine light comes on when cooling fans are running. (4/4)
 7/22/16 2:55am
Tsmooth68
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Vette(s):
1993 Chevrolet Corvette Base Edition. Exterior Color is Polo Green with Tan interior. 5.7 LT-1 V-8 with 4-speed automatic transmission.


Joined: 6/4/2016
Posts: 13

This ia a follow up on my original post. Thanks for the replies I gotten. The check engine light only comes on when the cooling fans comes on. I flashed the codes again, and they came up the same-codes 44 & 64. And, there were two new codes as well-55 & 63. Code 55 is engine running lean, but code 63 in the Chilton manual says that it can be a faulty ECM or ECM ground circuit. So, with that being said, the problem is the ECM. I already ordered the ECM from Rock Auto. I will keep you guys updated on what the outcome is. Thanks.

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