Trouble Codes???

Posted by John Eimer on

We get a lot of inquiries for our repair services from our customers. When we do, the first question we ask is what are the codes being sent by their vehicle? We hope the information below will give everyone a little insight as to why they are important and how to retrieve them. 
What are the trouble codes being sent by your vehicle and why are they important???
In many cases, when your vehicle has a diagnostic issue, a warning light will display on the dashboard. Some are self-explanatory, such as the oil light, others not so much. If the engine light appears, you'll need to run a diagnostic scan to determine which Onboard Diagnostics II (OBD2) trouble code is being sent. Turning away and acting as though nothing is wrong with your vehicle can further damage it. Find out more about the most common types of trouble codes and why they're sent. In addition, learn how to hook up the OBD2 trouble code tool to correctly diagnose the problem.

Information Collected by Trouble Codes

When a component exceeds the limits that are acceptable for the vehicle's operation, a trouble code is disbursed and saved in memory. This is needed to identify the exact problem.

OBD2 trouble codes are consistent in their format. They're always displayed as one letter followed by four numbers. The letter indicates the system where the issue is located.

  • B - The inside of the vehicle refers to the passenger area. Mostly comfort type components are covered as the B designation represents internal safety, such as seat belts and seating.
  • C - The chassis code is for the outside of the passenger area. Steering, brakes and more suspension mechanics are the main elements.
  • P - Transmission, engine and other powertrain components are indicated.
  • U - Shared computerized system-type functions that involve the integration of the network and vehicle are pointed out by this code.

The numbers that follow the letter of the diagnostic code has various meanings. For instance, if the first number placement after the letter is a zero "0", it's a generic fault message for OBD2 designations. These issues apply to a majority of vehicle manufacturers.

A number one "1" as the first number following the letter reveals that it is a manufacturer-based code for the vehicle's model or make.

The number two "2" or three "3" after the letter depends on the category as shown below:

Manufacturer-based issues

  • B2
  • C2
  • P3
  • U2
  • U3


  • P2

Here are a few codes you may run across:

  • P0401 Exhaust Gas Recirculation Flow Insufficient Detected
  • U0180 Data bus: automatic lighting control module - no communication
  • C0022 Brake Booster Solenoid (Subfault
  • B0052 Passenger Seatbelt Sensor (Subfault)

Many of the codes will actually display a description of the fault as to take much of the guesswork out. It's good to know though as much as possible just in case you're using a different OBD2 tool that supplies a written reason why an issue occurred. You can also search online for a specific code to get more information.

These steps are the same across the board; however, keep in mind that many OBD2 scan tools have their own specific instructions to follow so be sure to read those prior to using your scan tool.

How to use a OBD2 Diagnostic Scan Tool

  • Under the dashboard below the steering wheel, locate the connector to attach the OBD2 scan tool. The connector should have a pin shape that matches the end of the adapter on the scan tool.
  • Firmly attach the dongle (the computer connection adapter part end) of the OBD2 to the vehicle's connector.
  • Put the ignition key in the On position, but leave the engine off.
  • Check that the dongle is on. There may be a control switch for it.
  • Press the OBD2 tool Scan button if required.
  • Read the diagnostic trouble codes (DTCs) on the display screen of your OBD2 scan tool or use the have computer software or a mobile application that comes with your scanner if applicable.

When a dashboard fault light appears on your vehicle, don't hesitate to take action to resolve the issue. Even if the warning light temporarily disappears, use an OBD2 tool to diagnose it and you may curtail a more serious damaging problem later on down the line.

Share this post

← Older Post Newer Post →


  • Good day , I have a 2000 Jeep Wrangler with a 4.0L ; with 268420 miles on it , I have installed a New Crank Sensor ,Cam Sensor ,Fuel Pump , Coil pack and spark plugs , New Throttle Position Sensor ; the jeep will only run for about 10 minutes then it quits I’m thinking that something in the PCM is heating up. I can twist the key and the Jeep start back up , fuel pressure is 55psi. all the time
    Some times now it will post a P0340 code , it will clear some time when I restart the engine ?? Please Help !!

    Gary Forgey on
  • RncFTewyEk

    pjsnQMafvBoDXO on
  • yhkgHMovOLQBWK

    vJtxcankDquW on
  • eXfDIqCrEBWYyM

    zEFgqJcap on
  • ZpTenFBH

    nrTOsJak on

Leave a comment