Question about 1997 GMC Sierra
There are a lot of things that can cause this here are a few. The connector socket has come loose or the ground wire has ca-roded and is not making contact, here is what you can do clean both the battery posts with sand paper and clean the cable ends as well follow the ground cable and clean the ground on the frame and on the block, this is the most common problem, then get a paper clip with the key off place the paper clip on the #3 pin and the other end to ground now watch the check engine light and turn the key to the run position, not start, count the flashes, if it flashes like this flash pause flash flash that's code 12 it will flash 3 times next any trouble codes will flash and each trouble code will flash 3 times when t is done it will flash code 12 three more times and will resend the codes again, if you get no response from the computer then the computer e-prom may be bad or the computer is bad, if you need a new computer you must get the eprom and computer # and you need the vin number and you can go to schucks or auto zone and buy a refurbished computer and a updated eprom chip, be sure to disconnect the battery before working on the computer, the computer is located on the passenger side and you have to remove the kick panel, if not there follow the wiring harness as the engineers played peek a boo and hide and seek with the mechanics in those years so it could be anywhere. I re man computer will cost about $100.00 and if you don't live in a state where they have emissions laws you can buy a performance chip to get more power out out of your engine.
Posted on May 29, 2009
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Posted on Jan 02, 2017
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Dec 04, 2015 | Cars & Trucks
The ability of the control modules to communicate through the serial data circuit.
The identification of any stored diagnostic trouble codes (DTCs) and their status.
The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.
Diagnostic System Check - Engine Electrical
The numbers below refer to the step numbers on the diagnostic table.
Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
The symptom list in Symptoms will determine the correct diagnostic procedure to use.
The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
Did you perform the Battery Inspection/Test?
Go to Step 2
Go to Battery Inspection/Test
Install a scan tool.
Does the scan tool power up?
Go to Step 4
Go to Scan Tool Does Not Power Up in Data Link Communications
Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.
Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control System for a list of the power mode states that correspond to each ignition switch position.
Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?
Go to Step 4
Go to Power Mode Mismatch in Body Control System
Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit:
• The body control module (BCM)
• The driver information center (DIC)
• The instrument panel cluster (IPC)
• The powertrain control module (PCM)
Does the scan tool communicate with any module on the class 2 serial data circuit?
Go to Step 5
Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules have DTCs set.
Record all of the displayed DTCs the DTC status and the module which set the DTC.
Does the scan tool display any DTCs?
Go to Step 6
Go to Symptoms - Engine Electrical
Does the scan tool display any DTC beginning with "U"?
Go to Diagnostic Trouble Code (DTC) List in Data Link Communications
Go to Step 7
Does the scan tool display any DTC beginning with "B"?
Go to Diagnostic Trouble Code (DTC) List in Body Control Systems
Go to Diagnostic Trouble Code (DTC)
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The information below was complied by me, it explains what causes the check engine light to come on and the process of finding the cause.
When the Check Engine light (or Service Engine Soon) is turned on, the systems computer control unit (called the ECM) has sensed a fault in the electronic controls of the engine and/or the emission system. When this happens you will seldom feel the car engine run any different. There are about 50 possible system faults. To find out which one is causing a problem have the system scanned by a local shop with a MB compatible scan tool.
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