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.
Test sequence
- Test drive vehicle.
Observe the valid safety precautions when road testing → Safety precautions .
During the road test the following operating conditions must be fulfilled:
- The coolant temperature must exceed 85 ° C.
- When the temperature is reached, the operating conditions
- Idling
- Part throttle
- Enrichment
- Wide open throttle
- Overrun
- must be attained several times.
- Then:
- Continue running engine at idling speed.
- Connect Scan Tool VAG 1551 or Vehicle system tester VAG1552/. Start engine and select "Address word" 01 of engine control module: → 01 ON BOARD DIAGNOSTIC (OBD)
Indicated on display:
| Rapid data transfer HELP Select function XX |
- Press keys "0" and "4" for function "Initiate basic setting" and confirm entry with "Q" key.
Indicated on display:
| Basic setting Input display group number XXX |
- Press keys "0" , "0" and "1" for "Display group number 1" and confirm entry with "Q" key.
Indicated on display: (1...4 = display zones)
| System in basic setting 1 -> 1 2 3 4 |
Only continue with the test when:
- Coolant temperature is above 85 ° C - Display zone 2 -
- Change to display group 77 as follows:
- Press "C" key.
Indicated on display
| Basic setting Input display group number XXX |
- Press keys 0, 7 and 7 for "Display group number 77" and confirm entry with "Q" key.
- The engine must not be loaded during this diagnosis, if this occurs the diagnosis will be aborted and will not start again until the engine is revved-up.
Indicated on display: (1...4 = display zones)
| System in basic setting 77 -> 1 2 3 4 |
If the diagnosis is initiated by the engine control module the display in display zone 4 jumps from "Test OFF" to "Test ON".
- This process can take approx. 40 seconds.
- Leave engine running at idling speed until display zone 4 displays specification "Syst. OK.".
If "Syst. OK" appears in display zone 4:
- Press → key.
- Press keys "0" and "6" for function "End output" and confirm entry with "Q" key.
- Switch ignition off.
If "Syst.n.OK." appears in display zone 4:
- Press → key.
- Check DTC memory: → 01 ON BOARD DIAGNOSTIC (OBD)
- Read readiness code: → 01 ON BOARD DIAGNOSTIC (OBD)
- Generate readiness code again if DTC memory has been erased or engine control module disconnected from permanent positive supply: → 01 ON BOARD DIAGNOSTIC (OBD)
If no DTC is stored in DTC memory:
- Press keys "0" and "6" for function "End output" and confirm entry with "Q" key.
- Switch ignition off.
- Check combi-valve → Combi-valve, checking .
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.