On Board Diagnostics: OBD II

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On Board Diagnostics: OBD II

Postby tryg » Thu Nov 11, 2010 11:14 pm

Engine codes or On-Board Diagnostics (OBD) is a generic term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or a repair technician access to state of health information for various vehicle sub-systems. Some of our vehicles have PCMs/ECMs (they are also called body computers or the car's brain).

If you see a "check engine" light on your instrument cluster; your car has stored a diagnostic trouble code. Which means the computer system on your vehicle has detected a problem within various systems it controls. Your car has many different sensors that monitor the various vehicle systems. If the trouble code light has been illuminated your vehicle could enter into "limp mode" this means it might potentially run on a predetermined program that causes poor mileage and increased emissions.

An engine trouble code reader is an easy to use tool. All 1996 and newer vehicles utilize a "D" style plug-in connector that connects to the code reader.

Once the code reader is plugged in you can retrieve trouble codes the engine computer has stored in its memory, as well as clearing the trouble codes from the computer’s memory.

Connect your code reader to the under dash connector. The code reader will automatically turn on and prompt to start code retrieval. Once the code has been identified look up trouble code. Repair faulty item. After repair has been made clear trouble codes and recheck system.

**** I typed 'obd ii code reader' into a search on eBay and they started from, as low as, $15USD. Now, I am NOT saying that it is guaranteed to work for your car, you may have to do some independent research prior to making a purchase. Be warned! ****

How does the dealer do it?
The codes are stored in a mechanic's references, usually now they're electronic libraries. They can diagnose cars with a 'reader', basically an electronic device the same size as an electrical multimeter (the current Mitsubishi tool is the: MUT III).

The codes are stored in chapters, like a book, grouping like sensors together and any of their interpretations together;

Fault code library
Fuel air ratio P0100 - P0199
Fuel air ratio P0200 - P0298
Ignition P0300 - P0389
Emission control P0400 -P0492
Idle control, & inputs P0500 - P0570
Serial link & outputs P0600 - P0665
Transmission control P0700 - P0799
Transmission control PO800 - PO849

Breaking one out
OBD-II codes consist of a number of parts. Here is a sample OBD2 code:


Here is a breakdown of what each digit of the code means:

First Character - System
The first character identifies identifies the system related to the trouble code.

P = Powertrain
B = Body
C = Chassis
U = Undefined

Second Digit - Code Type
The second digit identifies whether the code is a generic code (same on all OBD-II equpped vehicles), or a manufacturer specific code.

0 = Generic (this is the digit zero -- not the letter "O")
1 = Enhanced (manufacturer specific)

Third Digit - Sub-System
The third digit denotes the type of sub-system that pertains to the code

1 = Emission Management (Fuel or Air)
2 = Injector Circuit (Fuel or Air)
3 = Ignition or Misfire
4 = Emission Control
5 = Vehicle Speed & Idle Control
6 = Computer & Output Circuit
7 = Transmission
8 = Transmission
9 = SAE Reserved
0 = SAE Reserved
Fourth and Fifth Digits

These digits, along with the others, are variable, and relate to a particular problem. For example,a P0171 code means P0171 - System Too Lean (Bank 1).

There are websites devoted to being massive libraries of engine codes, in fact, if you google:
Engine Codes, there is a website bearing just that name!

Although the list below is not all the possible codes, they are some unique to Mitsubishis;
P0137 MITSUBISHI Cylinder 1-4 Heated Oxygen Rear Sensor Circuit Low Voltage
P0171 MITSUBISHI Fuel Injection System Too Lean Bank 1
P0181 MITSUBISHI Fuel Temperature Sensor Circuit Range/Performance
P0182 MITSUBISHI Fuel Temperature Sensor Circuit Low Input
P0183 MITSUBISHI Fuel Temperature Sensor Circuit High Input
P0325 MITSUBISHI Knock Sensor Circuit Malfunction
P0421 MITSUBISHI Catalyst Efficiency Low Bank 1
P0500 MITSUBISHI Vehicle Speed Sensor Malfunction
P0506 MITSUBISHI Idle Control System RPM Lower Than Expected
P0507 MITSUBISHI Idle Control System RPM Higher Than Expected
P0508 MITSUBISHI Idle Air Control Valve Sense Circuit Low
P0509 MITSUBISHI Idle Air Control Valve Sense Circuit High
P0510 MITSUBISHI Accelerator Pedal Position (APP) Switch Circuit
P0513 MITSUBISHI Immobilizer Malfunction
P0516 MITSUBISHI Battery Temperature Sensor Circuit Low
P0522 MITSUBISHI Oil Pressure Too Low
P0532 MITSUBISHI A/C Pressure Sensor Circuit Low
P0533 MITSUBISHI A/C Pressure Sensor Circuit High
P0551 MITSUBISHI Power Steering Pressure Sensor Circuit Range/Performance
P0554 MITSUBISHI Power Steering Pressure Sensor Circuit Intermittent
P0562 MITSUBISHI Battery Low Voltage
P0563 MITSUBISHI System Voltage High
P0572 MITSUBISHI Brake Switch 1 Stuck On
P0573 MITSUBISHI Brake Switch 1 Stuck Off
P0581 MITSUBISHI Cruise Control Multifunction Input A Circuit High
P0582 MITSUBISHI Speed Control Vacuum Control Circuit
P0586 MITSUBISHI Speed Control Vent Control Circuit
P0594 MITSUBISHI Speed Control Servo Power Relay Circuit
P0600 MITSUBISHI Serial Communication Link
P0602 MITSUBISHI Control Module Programming Error
P0604 MITSUBISHI Internal Control Module RAM
P0605 MITSUBISHI Internal Control Module ROM
P0606 MITSUBISHI ECM Main Processor Malfunction
P0613 MITSUBISHI Internal Transmission Control Module
P0622 MITSUBISHI Generator FR Terminal Circuit Malfunction
P0627 MITSUBISHI Fuel Pump Relay Circuit
P0630 MITSUBISHI VIN Not Programmed or Mismatch
P0632 MITSUBISHI Odometer Not Programmed or Mismatch
P0633 MITSUBISHI SKIM Secret Key Not Stored In PCM
P0638 MITSUBISHI Throttle Actuator Control Range/Performance
P0642 MITSUBISHI Throttle Position Sensor Power Supply
P0643 MITSUBISHI Primary 5 Volt Supply Circuit High
P0645 MITSUBISHI Air Conditioning Clutch Relay Circuit Malfunction
P0652 MITSUBISHI Sensor Reference Voltage B Circuit Low
P0653 MITSUBISHI Sensor Reference Voltage B Circuit High
P0657 MITSUBISHI Throttle Actuator Control Motor Relay Circuit
'This car is more fun than the entire French Air Force crashing into a firework factory' - J. Clarkson
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