OBD-II codes can be really confusing since there are lots of different types and forms of trouble codes. Learn how to understand and SOLVE them!
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Reading car fault codes helps you understand why your check engine or other dashboard lights are illuminated. Here’s a quick guide:
- Connect Scanner to OBD Port:
The OBD port is usually under the dashboard on the driver’s side or in the interior fuse box. - Turn on the Ignition:
Ignition should be on, but the engine can be running. Avoid having both the engine and ignition off. - Read Codes:
Use the “read codes” or “scan” option on your scanner. Code readers display results instantly, while Bluetooth adapters may take a few minutes.
Types of Fault Codes:
- Confirmed Code: Set when a fault is detected and considered serious enough to be continuously active.
- Pending Code: Triggered if the fault is detected a certain number of times in a certain number of drive cycles.
- Permanent Code: A confirmed code that cannot be cleared using a scan tool; it clears only when the fault is resolved.
- Current Code: Indicates a diagnostic trouble code (DTC) test has failed during the current operation cycle.
- Historical Code: Set when a DTC is not pending, confirmed, or current, but the test has failed at least once since the last clearing.
Understanding the Codes:
The digits in the car scanner codes are not random! Every letter or digit in the code can give you extra information about your car’s malfunction.
| First Digit | Second Digit | Third Digit | Last Digits |
|---|---|---|---|
| P = Powertrain | 0 = Generic Code | 0, 1 = Fuel / Air Mixture | Description |
| B = Body | 1 = Manufacturer Specific | 2 = Fuel (Injector circuit) | Description |
| C = Chassis | 2 = Manufacturer Specific | 3 = Ignition | Description |
| U = Network | 4 = Exhaust / Emissions | Description | |
| 5 = Vehicle speed control / Idle | Description | ||
| 6 = Electronic control unit | Description | ||
| 7 = Transmission | Description | ||
| 8 = Transmission | Description | ||
| 9 = Transmission | Description | ||
| A, B, C = Hybrid | Description |
7-digits codes
Sometimes your code reader will show extra two zeros at the end. So the code P0420 is the same as code P042000. However, the last 2 digits in the 7-digit code c
Types of Fault Codes:
- Confirmed Code: Set when a fault is detected and considered serious enough to be continuously active.
- Pending Code: Triggered if the fault is detected a certain number of times in a certain number of drive cycles.
- Permanent Code: A confirmed code that cannot be cleared using a scan tool; it clears only when the fault is resolved.
- Current Code: Indicates a diagnostic trouble code (DTC) test has failed during the current operation cycle.
- Historical Code: Set when a DTC is not pending, confirmed, or current, but the test has failed at least once since the last clearing.
Understanding the Codes:
The digits in the car scanner codes are not random! Every letter or digit in the code can give you extra information about your car’s malfunction.
| First Digit | Second Digit | Third Digit | Last Digits |
|---|---|---|---|
| P = Powertrain | 0 = Generic Code | 0, 1 = Fuel / Air Mixture | Description |
| B = Body | 1 = Manufacturer Specific | 2 = Fuel (Injector circuit) | Description |
| C = Chassis | 2 = Manufacturer Specific | 3 = Ignition | Description |
| U = Network | 4 = Exhaust / Emissions | Description | |
| 5 = Vehicle speed control / Idle | Description | ||
| 6 = Electronic control unit | Description | ||
| 7 = Transmission | Description | ||
| 8 = Transmission | Description | ||
| 9 = Transmission | Description | ||
| A, B, C = Hybrid | Description |
7-digits codes
Sometimes your code reader will show extra two zeros at the end. So the code P0420 is the same as code P042000. However, the last 2 digits in the 7-digit code can further specify the problem.
00 = Not specified
04 = Open
11 = Short to ground
12 = Short to B+
13 = Open
14 = Short to the ground or open
15 = Short to B+
16 = Circuit voltage below the threshold
17 = Circuit voltage above the threshold
18 = Current below the threshold
31 = No signal
44 = Data memory failure
47 = Controller failure
49 = Internal electronic failure
51 = Not programmed
62 = Signal comparison failure
64 = Plausibility failure
72 = Actuator stuck closed
74 = Actuator slipping
77 = Commanded position not achievable
7E = Actuator stuck on
1A = Circuit resistance below the threshold
1C = Voltage out of range
1D = Current out of range
23 = Signal stuck low
24 = Signal stuck high
27 = Single rate of change above a threshold
29 = Performance signal invalid
2A = Stuck in range
2B = Signal cross coupled
2F = Signal erratic
7F = Actuator stuck off
85 = Signal above the allowable range
87 = Missing communication message
93 = Performance no operation
96 = Component internal failure
9C = Low insufficient flow
9E = Stuck on
Good job, lesson completed!
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I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko