Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic mode 3: Check DTC Memory
Function
This diagnostic mode indicates all stored DTCs of components and systems which are emission relevant.
Malfunction Indicator Lamp (MIL) in instrument cluster lights up for one DTC entry. Refer to Malfunction Indicator Lamp (MIL) in instrument cluster .
SAE Diagnostic Trouble Codes (DTCs)
The DTC always consists of a 5-digit alpha-numeric value with the following meaning:
| Component group: | |||||||
| P x x x x | DTC for drivetrain | ||||||
| Norm-Code: | |||||||
| P 0 x x x | DTCs defined by SAE with specified malfunction texts | ||||||
| P 1 x x x | Additional emission relevant DTCs provided by manufacturer | ||||||
| P 2 x x x | DTCs defined by SAE with specified texts, from MY 2000 | ||||||
| System group: | |||||||
| P x 0 x x | Fuel and air mixture and additional emission regulations | ||||||
| P x 1 x x | Fuel and air mixtures | ||||||
| P x 2 x x | Fuel and air mixtures | ||||||
| P x 3 x x | Ignition system | ||||||
| P x 4 x x | Additional exhaust regulation | ||||||
| P x 5 x x | Speed and idle control | ||||||
| P x 6 x x | Control module and output signals | ||||||
| P x 7 x x | Transmission | ||||||
| P x 8 x x | Transmission | ||||||
| P x 9 x x | Control modules, input and output signals | ||||||
Work procedure
- Connect diagnostic tester. Refer to Diagnostic tester, connecting .
- Start engine and let run at idle.
- Operate starter for approx. 6 seconds. Do not switch ignition off afterward.
- Under address word 33, select "Diagnostic mode 3: Check DTC memory."
The number of stored malfunctions or "0 malfunctions detected" is displayed.
- End diagnosis and switch ignition off.
- Repair stored malfunctions according to DTC table:
- SAE P0xxx-DTCs.
- SAE P1xxx-DTCs.
- SAE P2xxx-DTCs.
- Erase DTC memory. Refer to Diagnostic mode 4: Reset/erase diagnostic data .
- The DTC table is sorted by SAE codes.
- "Emission"-relevant malfunctions are additionally indicated in the instrument cluster via the Malfunction Indicator Lamp (MIL). Refer to Malfunction Indicator Lamp (MIL) in instrument cluster .
- In Diagnostic mode 2, it can be determined at which operating condition a malfunction was detected and stored by the control module for Diesel-Direct fuel injection system. Refer to Diagnostic mode 2: Check operating conditions .
- Erase DTC memory after repairing malfunction. Refer to Diagnostic mode 4: Reset/erase diagnostic data .
Display example:
P0183 Fuel Temperature Sensor -G81- Open circuit/short circuit to B+
Explanation:
- P0183 = SAE diagnostic trouble code (malfunction identification number).
- Fuel Temperature Sensor -G81- = faulty circuit or malfunctioning component.
- Open circuit/short circuit to B+ = malfunction type as text
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.