- Oxygen Sensor Check -
- Method (for both TestBook and Tee-in tool use):
Increase engine speed to 3000 r.p.m for approximately 30 seconds then allow to
idle, this is necessary to ensure oxygen sensor is at operating temperature.
voltage swings regularly between below 0.4 and above 0.6 volts, sensor is
- If reading is stuck high or low (see associated readings
detailed on poster) this will indicate sensor is not working.
- Oxygen Sensor voltage stuck high or low
- If engine has been idling or running at low rpm for long periods prior to test,
sensor may have become sooted, road test with engine speed held high in an
attempt to clean sensor without removal.
- If above fails to resolve condition, remove sensor and view tip, if still sooted,
carefully clean and refit to vehicle for re-test.
- If sensor voltage refuses to swing and remains high, fault may be rich mixture.
Check fuel return lines for kinks or restrictions or carry out fuel pressure
- If fuel system faults are eliminated and sensor refuses to swing correctly,
- Oxygen sensor testing - General
- If the system is working properly, the meter reading will switch regularly
between below 0.4v and above 0.6v. The actual meter readings are not too
important, the fact that it oscillates between low and high values is enough to
prove the system is working and hence, that fuelling is unlikely to be the cause
of any running problems.
- If during the test, readings did not oscillate but remained high, the mixture is
over rich. Check for kinks or restrictions in the fuel return line or use
TestBook to diagnose the fuel system. A constantly low reading could be due to
one of two things, either the fuelling is too weak, or the oxygen sensor is not
working. With the engine running, clamp the fuel return line for a maximum of 10
seconds, this will create an over rich mixture which in turn should prompt a
high voltage reading (above 0.6v) from the oxygen sensor.
- If this is the case
then check for a blocked fuel filter, kinked fuel feed line or any other
Note: Fuel hoses must be clamped for a short periods with approved Girling brake
hose clamp No. 64947017.