Display Group 026, 027 & 028

DISPLAY GROUP 026
Bank 1 Front Heated Oxygen Sensor (HO2S) 1, Voltage Signal Increase Or Decrease (response) Time.
DISPLAY GROUP 027
Bank 2 Front Heated Oxygen Sensor (HO2S) 2, Voltage Signal Increase Or Decrease (response) Time.
DISPLAY GROUP 028
Number Of HO2S Voltage Signal Increase and/or Decrease Tests.

NOTES:
^ If the value of the O2S diagnostic is NOT set to "0" in display field 1 of display group 023 during resetting of the Readiness Code, and/or if a malfunction (DTC) is stored in the DTC memory that affects the response time of the heated oxygen sensors, use display groups 026, 027 and 028 and display groups 036 and 037 to perform a selective diagnostic.
^ After each engine start, when the diagnostic conditions are fulfilled (see display group 036), the ECM checks the voltage signal increase and/or decrease (response) time of the front heated oxygen sensors (located in front of the Three Way Catalytic Converter (TWC).
^ The display values in display group 028 are increased by 1 each time a diagnostic is performed, no matter whether the diagnostic is recognized as OK or not OK. If the signal increase and decrease time is recognized as OK during the first diagnostic, the display values are increased by "1" and the diagnostic is ended. If the limit values (signal increase time: 70 ms, signal decrease time: 100 ms) are exceeded, the diagnostic is recognized as not OK and the malfunction "bank X Sensor Y signal too slow" is entered in the DTC memory The signal increase and signal decrease times continue to be checked, and the display values are increased by 1 with each additional diagnostic. However, the limit values can also be exceeded because of combustion misfiring. In this case, the DTC memory does not display the malfunction "O2S circuit slow response (Bx,Sx)", but instead "Cyl. X misfire detected".
^ Display groups 026 and 027 show the largest and smallest signal increase and/or signal decrease time of all the diagnostic tests performed, see display group 028. If during one of the subsequent diagnostic tests, a larger or smaller signal increase and/or signal decrease time is recognized, the existing value is superceded and the new value is displayed. If the diagnostic conditions are fulfilled, display group 037 shows the latest signal increase and/or signal decrease times. After ending diagnostic, the values displayed are those that were recognized during the last diagnostic test.
^ The display values are only reset by erasing the DTC memory. Selected observation periods can be defined by resetting the display values.

DISPLAY OVERVIEW

VAG 1551 Display Overview, Display Group 026:

Note: Display range is reset when the battery is disconnected, battery positive voltage (B+) supply to ECM is disconnected, or if DTC memory is erased.

VAG 1551 Display Overview, Display Group 027:

Note: Display range is reset when the battery is disconnected, battery positive voltage (B+) supply to ECM is disconnected, or if DTC memory is erased.

VAG 1551 Display Overview, Display Group 028: