Running Characteristics After Cold Start, Checking

Running Characteristics After Cold Start, Checking

If problems occur after a cold start, it is necessary to check whether they occur before or after the oxygen sensor control starts.

Oxygen sensor control starts when the required oxygen sensor temperature of approx. 300°C is reached.

The time which passes before this temperature is reached is influenced mainly by the following factors:
- Ambient temperature (summer/winter)
- Operating conditions after start
- Function of oxygen sensor heater

Test condition
- No DTCs are stored concerning oxygen sensor control, Querying DTC Memory Refer to Displaying and Reading Trouble Codes/With Manufacturer Scan Tool/DTC Memory Checking and Erasing DTC Memory Checking and Erasing

Test sequence
Test vehicle under cold start conditions in a road test.

NOTE: The road test requires a 2nd person.

WARNING! The scan tool must be secured to the rear seat and operated by a second technician from there.

- Connect V.A.G 1551 scan tool (VAG 1552). Start engine and select Engine Control Module (ECM) using address word 01. Refer to Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting V.A.G 1551 Scan Tool [1][2][3]Connecting VAG 1551 Scan Tool

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press -Q- button to confirm input.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press 0, 3 and 1 for the function "display group number 31", and then press Q to exit from input mode.

Indicated on display (1 - 4 = display fields)

Read Measuring Value Block 31 ->
1 2 3 4

- Now perform road test and observe oxygen sensor voltage in display fields 1 (sensor 1) and 3 (sensor 2).

When vehicle is cold or when oxygen sensor control is not operating, voltage should be: 0.45-0.50 V
When oxygen sensor control starts, voltage signal in display fields 1 and 3 should oscillate between 0.0-1.1 V.

Read Measuring Value Block 31 ->
1 2 3 4

NOTE:
- Voltage values over 0.7 V mean that mixture is rich.
- Voltage values below 0.3 V mean that mixture is lean.

If the problems with running characteristics occur before the oxygen sensor control starts:

The cause cannot be in oxygen sensor control.

NOTE:
- If the problem gets better after the oxygen sensor control starts, the cause (for example, unmetered air, faulty fuel injector, etc.) is counteracted by the intervention of the control. This can be recognized by reading the oxygen sensor adaptation values.
- Display group 99 can be used to turn oxygen sensor control off and on for specific purposes. Pressing buttons 4 and 8 switches back and forth between "Basic setting" (oxygen sensor control off) and "Read Measuring Value Block" (oxygen sensor control on).

If the problems with running characteristics occur only after oxygen sensor control starts:
- Test Heated Oxygen Sensors (HO2S) and oxygen sensor control. With Manufacturer's Scan Tool