Question about 1997 GMC Sierra

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CHECK ENGINE LIGHT Check engine light is on. System will not connect to scan tool. No other symptoms.

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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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I have a 2004 envoy xuv and my service 4wd light came on but I don't have any lights on the switch and it won't change into anything and I don't hear anything trying to engage and lights don't blink

The Automatic Transmission Diagnostic System Check is an organized approach to identify a problem created by an automatic transmission. The Diagnostic System Check - Engine Controls in Engine Controls - 4.2L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L and 6.0L is the diagnostic starting point for an automatic transmission complaint. The Diagnostic System Check - Engine Controls in Engine Controls - 4.2L or Diagnostic System Check - Engine Controls in Engine Controls - 4.8L, 5.3L and 6.0L directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveability complaint or if you have been directed here from another service information section.
Follow the table to help reduce diagnostic time and help prevent unnecessary replacement of good parts.
  1. Install a scan tool.
  2. Important: Check for applicable service bulletins before proceeding with this test. Perform this test only if there is a driveability complaint or if you have been directed to this table from another section in the service information.
    Important: Do not turn the ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure.
  3. Turn ON the ignition, with the engine OFF.
Does the scan tool turn ON?
Go to Step 2
Go to Diagnostic Starting Point - Data Link Communications in Data Link Communications

Is the MIL ON?
Go to Step 3
Go to Malfunction Indicator Lamp (MIL) Inoperative in Engine Controls - 4.2L or Malfunction Indicator Lamp (MIL) Inoperative in Engine Controls - 4.8L, 5.3L and 6.0L

Attempt to establish communication with the PCM controller module or modules.
Does the scan tool communicate with the PCM control module or modules?
Go to Step 4
Go to Diagnostic Starting Point - Data Link Communications in Data Link Communications

Important: Diagnostic Trouble Codes (DTCs), engine performance, and transmission default actions can greatly affect the transmission performance. Ensure that these items are not the cause of a transmission concern.
Use the scan tool Capture Info function in order to save or capture (Store Info) any DTC Information.
Are there any DTCs present?
Go to Diagnostic Trouble Code (DTC) List/Type
Go to Symptoms - Automatic Transmission
Your best bet is take to transmission repair shop or the dealer

Dec 04, 2015 | Cars & Trucks

1 Answer

2002 chevy silverado trys to stall in any condition sometime it will stall. all dash light will come on. starts right up.

Is check engine light Lit ? You should have all the computers on the vehicle check for DTC'S - diagnostic trouble codes ! Check the battery an all connections !
Diagnostic Starting Point - Engine Electrical
Begin the system diagnosis with the Diagnostic System Check - Engine Electrical . The Diagnostic System Check will provide the following information:
The identification of the control module(s) which command the system.

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
Test Description
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)

Oct 28, 2015 | Cars & Trucks

1 Answer

I replaced the alternator on my 1999 Audi A6 with 2.8 engine. Now the check engine light is on. Was not on prior to the repairn. How do I correct?

Instructions on How to Turn Off The Check Engine Light:
Step 1. If not using a scan tool, locate your vehicle's battery. Disconnect the 12v positive cable (red wire) from battery terminal (+). Leave it disconnect for 5 minutes. While the battery is disconnected, cycle the ignition switch to ON position 3 times. If using a scan tool to turn off the check engine light, follow manufacturers directions. You will need to find your vehicle's OBD II Data Link Connecter (DLC) and connect your scan tool to the DLC, then follow the steps indicated on your scan tool or scan tool manual.

Step 2. Insure ignition switch is OFF. Reconnect the battery 12v positive cable (red wire) to battery terminal (+).

Step 3. Cycle ignition switch to ON position and wait 1 minute, then start your vehicle. Check Engine Light or Service Engine Soon Light should be reset and turned OFF.

Step 4. Drive your vehicle for one week under normal driving conditions. During this period the emissions computer is gathering data and re-learning your vehicle's emissions components and systems. The emissions computer OBDII (on-board diagnostics) system must complete at least one drive cycle (in some cases two or three). A drive cycle is a sequence of internal tests which the emissions computer runs while your vehicle is being driven. This insures all emissions systems are functioning properly. Proper "readiness flags" are set as the computer completes it's cycles. Test cycles are unique to a vehicle. Certain cycles run under very strict parameters, and may require extended driving time to trigger on. Cycle data and readiness flag information is available through your dealership's service department. The data vary widely.

Sep 15, 2014 | 1999 Audi A6

1 Answer

2005 Dakota will not stay running

Here are some tests you can try. The list is generic and you may have tried some of these already. It sounds like a vacuum line issue to me. For other info try this website:

Repair Guides Symptom Diagnosis no Codes What To Do When There Are No...

Preliminary Checks
Prior to starting this symptom test routine, inspect these underhood items:
  1. All related vacuum lines for proper routing and integrity.
  2. All related electrical connectors and wiring harnesses for faults (Wiggle Test).
  3. Check the throttle linkage for a sticking or binding condition.
  4. Air Intake system for restrictions (air inlet tubes, dirty air filter, etc.).
  5. Search for any technical service bulletins related to this symptom.
  6. Turn the key to off. Unplug the MAP sensor connection and restart the engine to recheck for the idle concern. If the condition is gone, replace the MAP sensor.

Test 2: Rough, Low or High Idle Speed Condition (Continued)
Test 2 Chart
Step Action Yes No 1 Step Description: Verify the rough idle or stall Does the engine have a warm engine rough idle, low idle or high idle condition in P or N- Go to Step 2. Fault is intermittent. Return to the Symptom List and select another fault. 2 Step Description: Verify idle speed & timing Verify the base timing is within specifications Verify that the base idle speed is set properly Are the timing and idle speed set properly- Go to Step 3. Set the base idle speed and timing to the specifications and then retest for the symptom. 3 Step Description: Check AIS / IAC Operation Check the AIS or IAC motor operation Inspect the AIS/IAC housing in throttle body for restricted passages. Clean as needed. Set the parking brake, block the drive wheels and turn the A/C off. Install the Scan Tool. IAC Motor Tester - Turn the key off and then connect the IAC tester to the IAC valve. Start the engine and use the IAC tester to extend and retract the IAC valve. ATM Test - Start the engine. Use the tool to change the speed from min-idle to 1500 rpm. Did the idle speed change as commanded- Install an Aftermarket Noid light and check the operation of the PCM and AIS or IAC motor circuits. Check the motor for signs of open or shorted circuits. Replace the IAC motor or PCM as needed or make repairs to the IAC motor wiring. If all are okay, go to Step 4. If the AIS/IAC motor passages are clean and engine speed did not change as described when the AIS/IAC motor was extended and retracted, replace the AIS/IAC motor. Then retest for the condition. 4 Step Description: Check/compare PID values Connect Scan Tool & turn off all accessories. Start the engine and allow it to fully warmup. Monitor all related PIDs on the Scan Tool. Verify the P/N switch input in gear and Park. Check the O2S operation with a Lab Scope. Are all PIDs within normal range- Go to Step 5. Note: An IAC motor count of over 80 indicates the pintle is extended and an IAC count of (0) indicates the pintle is retracted. One or more of the PIDs are out of range when compared to "known good" values. Make repairs to the system that is out of range, then retest for the symptom. 5 Step Description: Check the Ignition System Inspect the coils for signs of spark leakage at coil towers or primary connections. Check the spark output with a spark tester. Test Ignition system with an engine analyzer. Were any faults found in the Ignition system- Make repairs as needed Go to Step 6. 6 Step Description: Check the Fuel System Inspect the Fuel delivery system for leaks. Test the fuel pressure, quality and volume. Test the operation of the pressure regulator. Were any faults found in the Fuel system- Make repairs as needed Go to Step 7. 7 Step Description: Check the Exhaust System Check Exhaust system for leaks or damage. Check the Exhaust system for a restriction using the Vacuum or Pressure Gauge Test (e.g., exhaust backpressure reading should not exceed 1.5 psi at cruise speeds). Were any faults found in Exhaust System- Make repairs to the Exhaust system. Then retest the symptom. Go to Step 8. Repair Guides Symptom Diagnosis no Codes What To Do When There Are No...

Mar 20, 2014 | 2005 Dodge Dakota Quad

3 Answers

Check engine light

sometimes you don't put the gas cap on properly, the sensor will put check engine light on. Go and check the gas cap.

Oct 27, 2013 | 2006 Pontiac Grand Prix

1 Answer

Have 97 geo wants to cutout and die in gear no power idles fine and rev up fine

nice posted symptoms.
all suzuki engines use 1 of 2 ways to measure air flow in to the engine.
3 engines used, 1.0L , 1.3L and 1.3L 16v , each have a different EFI system.
no matter, as scan tool will show you if the air flow reading are wrong.
the first low power, check is fuel pressure, if not at spec, say at 10psi (low)
then there will be no power.
if the engine you have has a MAF sensor and is dead, that will cause
limphome and low power.
the first check is, keyon, check engine light, is it on ?
if lamp glows key on, but does not go out running , then the ECU
has stored, errors. in the memory, DTC memory, you need a scan tool
to find this error. they cost $50 or have a shop scan it .

Apr 11, 2013 | 1997 Geo Metro

1 Answer

Check Engine Light

If concern which illuminated the check engine light is repaired the code should go innactive in the vehicle ECM and it will and turn off the light after a certain amount of hours or drive cycles.. If you do not want to wait for that you can connect to the car with an OBD2 scan tool and reset them with the scan tool.

Sep 24, 2012 | 2003 Nissan Altima

1 Answer

Yellow indicator light on dash of 560 sec

This is the emissions system warning light, commonly referred to as the "Check Engine" light.
Please read on.

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.

Sep 25, 2011 | 1991 Mercedes-Benz 560

2 Answers

Check engine light and vsc trac off lights stay on. Cannot turn svc off by pressing button on Dash

Hi, have you scanned the vehicle to see why your check engine light is on? IF no, you need to. Toyota/Lexus computer system illumniates both engine light and VSC lights whenver a fault occurs in either unit. VSC or stability control is like trac-control or ABS braking system. Get car scanned and make sure all computers are scanned for additional codes, repair them first reset lights and test drive. ON a side note, fixing check engine light will usually take VSC light away also, however sometimes the VSC system will glitch out and a Steering Angle relearn is necessary, it takes about 3mins to perform and a good quality scan tool with 2004 current software. Good Luck.

May 16, 2011 | 2004 Toyota RAV4

2 Answers

Check engine light staying on

No,  the check engine lamp will only come on when there is a problem in engine management system, it needs to be checked with an OBDII scan tool to find the problem causing the check engine lamp to come on.

Nov 25, 2008 | 2003 Toyota Corolla

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