OBD-II Diagnostic Trouble Codes (DTC's) For OBD-II (OBD2) equipped General Motors (GMC, Chevrolet, Buick, Oldsmobile, Cadillac, Pontiac, Saturn) vehicles. Identifying OBD II Equipped cars All cars and light trucks built and sold in the United States after January 1, 1996 were required to be OBD-II equipped. In general, this means all 1996 model year cars and light trucks are compliant, even if built in late 1995. Some 1995 model year vehicles are also equipped with OBDII - although some pre-1996 OBD-II cars are not 100% compliant. Pre-OBD-II cars had connectors in various positions under the dashboard and under the hood. All OBD-II cars have a connector located in the passenger compartment easily accessible from the driver's seat. Communications Protocols GM cars and light trucks use SAE J1850 VPW (Variable Pulse Width Modulation). There are some variations among imports such as the Cadillac Catera, which is a German Opel derivative, the Catera uses the European ISO 9141 protocol. Reading OBD II codes A cable is plugged into the OBD-II J1962 connector and the other end is connected to a scan tool. A hand-held scan tool is usually limited to one OBD-II system type - there are three basic OBD-II protocols in use, each with minor variations on the communication pattern between the on-board diagnostic computer and the scan tool. In general, Chrysler products and all European and most Asian imports use ISO 9141 circuitry. GM cars and light trucks use SAE J1850 VPW (Variable Pulse Width Modulation), and Fords use SAE J1850 PWM (Pulse Width Modulation) for communication. General Motors Driving Cycle A complete driving cycle will perform diagnostics on all monitored systems and can usually be completed in less than fifteen minutes. Performing a GM OBD-II Driving cycle: Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 122�F (50�C) and within 11�F (6�C) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed. Accelerate. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3. Hold Steady Speed. Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears. Disecting a DTC How the Diagnostic Trouble Code is created: A DTC is made up of 5 digits. The chart below shows the composition of a DTC. With this information you can easily determine what system to trouble shoot without knowing the exact description of the code. X X X X X | | | | | | | | B Body ----------+ | | +-- Fault (00 to 99) C Chassis -------+ | | P Powertrain ----+ | | U Network -------+ | +------ 1 Fuel & Air Metering | +------ 2 Fuel & Air Metering (Injector) | +------ 3 Ignition System or Misfire 0 SAE --------------+ +------ 4 Auxiliary Emission Controls 1 MFG --------------+ +------ 5 Vehicle Speed & Idle Control System +------ 6 Computer Output Citcuit +------ 7 Transmission +------ 8 Transmission +------ 9 Reserved +------ 0 Reserved Types of DTC's There are two categories of DTC's that apply to OBD-II. Type A Emissions related. Requests illumination of the MIL after one failed driving cycle. Stores a freeze frame DTC after one failed driving cycle. Type B Emissions related. Sets a Pending Trouble Code after one failed driving cycle. Clears a Pending Trouble Code after one successful driving cycle. Turns on the MIL after two consecutive failed driving cycles. Stores a freeze frame after two consecutive failed driving cycles. GM Diagnostic Trouble Code List Manufacturer Codes: DTC 01 General Sensor Fault DTC 02 Instantaneous Battery Voltage Out of Range DTC 03 Filtered Battery Voltage Out of Range DTC 04 Compressor Relay Short to Ground/Open DTC 05 Compressor Relay Short to Battery DTC 06 Exhaust Valve Short to Ground/Open Circuit DTC 07 Exhaust Valve Short to Battery DTC 08 Warning Lamp Short to Ground/Open Circuit DTC 09 Warning Lamp Short to Battery DTC 10 Inside Air Temperature Sensor Voltage Low DTC 10 Intake Accumulator Fault DTC 11 Driver Seat Forward/Backward Motor Inop DTC 11 Exhaust Accumulator Fault DTC 11 Inside Air Temperature Sensor Open Circuit DTC 11 Transponder Key Problem DTC 12 Consecutive Intake Malfunction DTC 12 Driver Seat Recliner Motor Inoperative DTC 12 LH Air Outlet Sensor Voltage Low DTC 12 Wrong Transponder Key DTC 12 Diagnostic System Check (Escalade) DTC 13 Driver Air Bag Deployment Loop Short to GND DTC 13 Immobilizer Not Programmed DTC 13 LH Air Outlet Sensor Open Circuit DTC 14 Coolant Temp Voltage Low DTC 14 Driver Pretens Deployment Loop Short to GND DTC 14 No Transponder Key Programmed DTC 14 RH Air Outlet Sensor Voltage Low DTC 15 Driver Air Bag Deploy. Loop Short to V DTC 15 RH Air Outlet Sensor Open Circuit DTC 15 Vehicle Speed Signal Voltage Low DTC 16 Driver Pretens Deploy Loop Short to Voltage DTC 16 Driver Seat Front Height Motor Inoperative DTC 16 Int Air Mix Door Mtr Volts Low/Open Circuit DTC 16 Vehicle Speed Signal Voltage High DTC 17 Driver Seat Rear Height Motor Inoperative DTC 17 Interior Air Mix Door Motor Voltage High DTC 17 No Engine Request Received DTC 18 Driver Side Mirror Circuit DTC 18 LH Air Mix Door Mtr Volts Low/Open Circuit DTC 18 MIL Circuit DTC 19 Inside Mirror Circuit DTC 19 LH Air Mix Door Motor Voltage High DTC 20 Passenger Side Mirror Circuit DTC 20 RH Air Mix Door Mtr Volts Low/Open Circuit DTC 21 Driver Seat Adjuster Switch Inoperative DTC 21 No Speed Signal DTC 21 RH Air Mix Door Motor Voltage High DTC 21/31 Courtesy Lamps Feed Shorted to Ground (Escalade) DTC 22 Floor Air Mix Dr Mtr Voltage Low/Open CKT DTC 22 Solenoid Circuit Short to Ground/Open DTC 22/32 Courtesy Lamps Return Shorted to Battery (Escalade) DTC 23 Floor Air Mix Door Motor Voltage High DTC 23 Pass. Air Bag Deployment Loop Short to GND DTC 23 Power Steering Control Module Malfunction DTC 23/33 RAP Feed Shorted to Ground or Battery (Escalade) DTC 24 Def Air Mix Door Mtr Volts Low/Open Circuit DTC 24 Pass. Pretens Deployment Loop Short to GND DTC 24/34 Seatbelt Indicator Shorted to Ground or Battery (Escalade) DTC 25 Defrost Air Mix Door Motor Voltage High DTC 25 Pass. Air Bag Deploy. Loop Short to Voltage DTC 25/35 Security Indicator Status (Escalade) DTC 26 Pass. Pretens Deploy. Loop Short to Voltage DTC 27 Blower Motor Voltage Low or Open Circuit DTC 28 Air Circ. Valve Voltage Low or Open CKT DTC 29 Air Circulation Valve Voltage High DTC 30 Heating Cut-Off Valve Volts Low or Open CKT DTC 31 Driver Air Bag Deploy. Loop Resistance High DTC 31 Heating Cut-Off Valve Voltage High DTC 32 Driver Air Bag Deploy. Loop Resistance Low DTC 32 Rear Window Defog Signal Voltage Low DTC 33 Pass. Air Bag Deploy. Loop Resistance High DTC 33 Rear Window Defog Signal Voltage Open CKT DTC 34 Pass. Air Bag Deploy. Loop Resistance Low DTC 34 Rear Window Defogger Open Circuit DTC 35 A/C Request Signal Voltage High DTC 35 Driver Pretens Deploy. Loop Resistance High DTC 36 A/C Request Signal Voltage Low DTC 36 Driver Pretens Deploy. Loop Resistance Low DTC 37 Heater and A/C Control Switch Stuck DTC 37 Pass. Pretens Deploy. Loop Resistance High DTC 38 Pass. Pretens Deploy. Loop Resistance Low DTC 38 Solar/Twilight Sensor Supply Voltage Low DTC 39 Solar/Twilight Sensor Supply Voltage High DTC 40 Solar/Twilight Sensor GND Short to Voltage DTC 41 Last Message Received Valid (Escalade) DTC 42 Last Message Received Invalid (Escalade) DTC 43 Last Message Received with Sumcheck Error (Escalade) DTC 43 Warning Lamp Circuit Short to Voltage DTC 44 Warning Lamp Circuit Open or Short to GND DTC 44 Last Message Received with Encryption Error (Escalade) DTC 45 Receiver Processing in 20 Second Lockout (Escalade) DTC 50 Seat Adjuster Memory Module Malfunction DTC 50, 51, or 55 Sunroof Actuator Malfunction DTC 51 Replace Heater and A/C Control DTC 51 Reprogram Cluster or Cluster Malfunction DTC 52 Heater and A/C Control Not Programmed DTC 52 Reprogram Cluster DTC 52 SDM Not Configured DTC 53 Configuration Mismatch DTC 55 Internal SDM Failure DTC 55 Replace Heater and A/C Control DTC 55 Seat Adjuster Memory Module Malfunction DTC 55 Theft Deterrent Module Malfunction DTC 55 Begin Configuration Display (Escalade) DTC 56 SDM Not Reusable DTC 65 Passenger Air Bag Deployment Commanded DTC 66 Driver Air Bag Deployment Commande...
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