Tip & How-To about Chevrolet Blazer

OBD1 Trouble codes, without a scan tool.

Here is a tip for retrieving Diagnostic Trouble Codes (DTCs) from any OBD1 GM vehicle.

First thing is your going to need to get a paper clip, and bend it into a U shape.

Now stick the ends of the paper clip into the 2 top right hand side holes in the connector. Note: Do this with the key in the run position, but with the engine off.

You should now see your check engine light flash once, pause, then 2 times. This indicates that your ECM is working properly.

Now it will blink indicating your code. For example an EGR failure code is DTC 32. You will see your light blink 3 times, pause, then blink 2 times, giving you code 32.

A list of codes can be found here: http://www.gmtuners.com/OBD1_DTC.htm.

Hopefully this helps some of you all out there. Thanks for looking.

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1 Answer

2004 ford expedition eddie bauer All the doors won't lock/unlock, just make a buzzing sound repeatedly. Also does this when shutting the vehicle off.


What makes a buzzing sound , the door lock actuators ? Or where do you hear the buzzing coming from if not at the doors ?
Power Lock
The power lock/unlock feature requests all of the vehicle doors, including the liftgate, be locked or unlocked upon a customer request from any interior door lock switch in the vehicle. The power door locking system functions independently of ignition status or vehicle speed. When the vehicle security module receives an unlock/lock command from any door lock control switch, the vehicle security module will activate relays internal to the module to supply the correct power and grounds for the door lock actuators.
Visual Inspection Chart Mechanical Electrical
  • Binding latches
  • Central junction box (CJB) fuse(s):
    • 5 (7.5A)
    • 30 (30A)
  • Circuitry
  • Relays
  • Remote transmitter
  • Keyless entry keypad
  • Vehicle security module

  1. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
  1. If the diagnostic tool does not power up, refer to the diagnostic tool manual.
    1. Carry out the diagnostic tool data link test. If the diagnostic tool responds with:
      • SCP, UBP or ISO; all elctrconic control unitw, no response/not equipped, refer to Section 418-00 .
      • No response, not equipped for vehicle security module, refer to Section 419-10 .
      • System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs, and carry out the self-test diagnostics for the vehicle security module.
    1. If the DTCs retrieved are related to the concern, go to the Vehicle Security Module Diagnostic Trouble Code (DTC) Index to continue diagnostics.
    1. If DTCs are retrieved that are not found in the following Vehicle Security Module Diagnostic Trouble Code (DTC) Index, refer to the Master Vehicle Security Module Diagnostic Trouble Code (DTC) Index in Section 419-10 .
    1. If no DTCs related to the concern are retrieved, proceed to the Symptom Chart to continue diagnostics.

Jan 13, 2016 | Ford Cars & Trucks

1 Answer

dome lights stay on all the time


Hey Rich how's it going ? What make , model an year vehicle do you have ? On vehicles after 1996 light functions are control by a control module , Body control module for GM vehicles , GEM - generic electronic module an smart junction box for Ford vehicles an Chryslers have central timer modules or upfront modules or now they have totally intergraded power module . These modules receive an input from a door switch or the switch on the dash ! anything is possible with these systems ! Do you have a symbol of a car on the dash showing a door open when it's not ? A door ajar message ? I have my Ford service info open on my lap top , was check out a problem on ford explorer , have a description on GEM .
Detecting Faults in the GEM Output Circuits
Battery shorts can only be detected when the device being controlled is actuated (e.g., relays, lamps or solenoids). All faults are monitored continuously during the vehicle operation. Reporting Trouble Codes
Faults are displayed after the continuous DTCs and the On-Demand DTCs are retrieved. Continuous DTCs should be retrieved from the GEM before an On-Demand Self Test is run. These DTCs are then compared against the diagnostic trouble codes retrieved after running an On-Demand Self Test. .
An a code reader for check engine lights won't work for these systems !
A code

Mar 20, 2015 | Cars & Trucks

1 Answer

i have a 1993 chevy k1500 5.7 liter 4wd with a 40L60E transmission and it will not shift out of 2nd gear what could the problem be


Your truck could be on a limp mode since your transmission is controlled by the ECM. 
Here is a way for you to retrieve the fault codes in the ECM that is keeping your transmission from shifting past 2nd gear. Just be careful not to burn out the transmission.
On board diagnostic (OBD) was designed on vehicles equipped with electronic fuel injection so you can generally retrieve the codes yourself. No need buying a scanner or running to any parts stores to check the engine light. This system is called obd1 and applies to most vehicles made before 1995 for domestics and 1993 on imports. 

For GM domestic vehicles made before 1995, the diagnostic connector is located under the dash panel by the driver side. To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.

For GM and domestic vehicles and most of the codes can be erased or cleared by disconnecting the battery negative terminal for 1 minute and reconnect. Just make sure to check your service manual in case you have electronic equipment such as radio or clock that needs reprogramming in which battery disconnection is not recommended. Finally after performing repairs on the culprit code, always go for a road test to confirm if the problem is fixed.

Good luck and here is a link for the OBD 1 codes. http://chevythunder.com/199295_lt1_trouble_codes.htm#Code 28

May 03, 2009 | Chevrolet 1500 Cars & Trucks

1 Answer

low idel rough


You could have a Air Idle Control valve or sensor problem. Your going to have to scan the ECM to find out if it is your (IAC).
Here is how to check your ECM for Codes. 
On board diagnostic (OBD) was designed on vehicles equipped with electronic fuel injection so you can generally retrieve the codes yourself. No need buying a scanner or running to any parts stores to check th3 Engine Light. This system is called obd1 and applies to most vehicles made before 1995 for domestics and 1993 on imports. In this article, I will discuss the methods used by domestic vehicle manufacturers on how to check the engine lights in their cars and trucks.
For GM domestic vehicles made before 1995, the diagnostic connector is located under the dash panel by the driver side. To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.
The codes can be erased or cleared by disconnecting the battery negative terminal for 1 minute and reconnect. Just make sure to check your service manual in case you have electronic equipment such as radio or clock that needs reprogramming in which battery disconnection is not recommended. Finally after performing repairs on the culprit code, always go for a road test to confirm if the problem is fixed.
Good Luck and here is a link for gm codes.http://chevythunder.com/199295_lt1_trouble_codes.htm#Code

May 02, 2009 | Chevrolet C1500 Cars & Trucks

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