Autodata - Diagnostic Trouble Codes Fault locations and probable causes - 2004 edition

Oxygen sensor (02s)
NOTE: The following voltage figures refer to the almost universally usedzirconium type O2S, without a 0,5 V control reference. A
few recent models are fitted with a Titanium sensor which has an operating range of 0-5 volts and shows a high voltage
signal with a weak mixture and a low voltage signal with a rich mixture.
Connect oscilloscope test probes between oxygen sensor ECM pin and earth.
Ensure engine is at normal operating temperature.
Compare scope trace with wave form reference Fig. 27.
If the trace shows no wave form but instead is a straight line, this usually indicates a weak mixture if the voltage is
approximately 0-0,15, or a rich mixture if the voltage is approximately 0,6-1 - refer to Autodata fuel injectiontengine
management manuals or CD for possible causes of this condition.
If the wave form is satisfactory at idle, open the throttle briefly several times in succession.
The wave form should show the signal voltage 'cycling' between approximately 0-1 Volt.
The increasing voltage corresponds to the engine speed rising and the decreasing voltage corresponds to the engine
speed falling.
Knock sensor (KS)
Connect oscilloscope test probes between knock sensor ECM pin and earth.
Ensure engine is at normal operating temperature.
Briefly snap throttle open.
Wave form should display an AC signal showing a considerable increase in amplitude Fig. 28.
If this signal is not distinctly displayed, tap the cylinder block lightly in the region of thesensor.
If the signal is still not satisfactory this indicates a faulty sensor or associated circuit.
Fig. 27 Fig. 28