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1994 Suburban sevice engine light comes on


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pup50
New User

Jul 11, 2014, 6:46 AM

Post #1 of 3 (1153 views)
1994 Suburban sevice engine light comes on Sign In

This is an intermittent problem. My service engine light will come on and the engine will idle up. When this happens the tranny shifts hard and at high rpms. Strange thing is if I turn the vehicle off and restart the problem disappears but may return as I'm driving down the road. This rarely happens when I first start it in the morning for work. A friends '96 had the same basic problem and it was the Idle Control Valve. Could this be my problem as well?


Hammer Time
Ultimate Carjunky / Moderator
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Jul 11, 2014, 7:35 AM

Post #2 of 3 (1137 views)
Re: 1994 Suburban sevice engine light comes on Sign In

To extract a trouble from the computer for diagnostic purposes, the Assembly Line Communication Link (ALDL) connector is used.
Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.
After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.


ALDL Connector (Located Underdash)


The ALDL diagnostic connector is located in the passenger compartment.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 11, 2014, 11:42 AM

Post #3 of 3 (1125 views)
Re: 1994 Suburban sevice engine light comes on Sign In

Get code for the '94 as Hammer Time suggested and forget something similar with another car never mind a '96 and newer for diagnosing this way.


I think this has a cable to kick down shifts from throttle body to transmission that might be sticking - at least take a look and lube it as best you can,


T







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