O2 Sensor - Diagnosis Update

87mazda06

Category Applicable Model/s Subject Bulletin No. 029/87
4 1987 & 1988 B2200 O2 SENSOR Issued 8/31/87
Revised

DESCRIPTION

Because the O2 sensor fluctuates over a wide range of readings, a specified time (3 minutes) has been allowed to determine a failure. This delay in the failure code eliminates premature and misleading codes.

Previous units (1986 B2000) could indicate a failed O2 sensor under certain circumstances without any problem existing. This condition could have occurred under the following examples:

1. Engine kept idling for extended periods.

2. High ambient air temperature causing excessive fuel vapors.

3. If duty is fluctuating at the high end of the range.

The 1987 B2200 control unit is capable of detecting some intermittent failures and storing these in memory until retrieved. To simulate a failed O2 sensor, follow the procedure below.


Simulation of Failed O2 Sensor Procedure

1. Bring engine to operating temperature.

2. Turn engine "off".

3. Disconnect the O2 sensor connector.

4. Restart engine. Hold the engine RPM at 1500 or more for 3 minutes (time is very important). After 3 minutes, trouble code 15 should be indicated and fail-safe will fix duty at 20%.

5. After the simulation test, clear memory by disconnecting the negative battery cable and apply the brake to clear the control unit memory.