02 Sensor Voltage via Scan When Sensor is Unplugged

[GA_TMAC]

Hi All,

I have an 1987 R10 5.0 with THM400 trans. The ECM appears to be working OK. I can get code 12 and I can disconnect the coolant sensor and it throws the code. My question is (when using Win ALDL) should the scan tool (more properly the ECM) be reporting/seeing any voltage if the 02 sensor is disconnected? IF the O2 sensor is unplugged, should it throw a code? Thanks in advance

GA_TMAC

[GA_TMAC]

Please help ... great forum!

[rfmaster]

Originally Posted by GA_TMAC

Hi All,

I have an 1987 R10 5.0 with THM400 trans. The ECM appears to be working OK. I can get code 12 and I can disconnect the coolant sensor and it throws the code. My question is (when using Win ALDL) should the scan tool (more properly the ECM) be reporting/seeing any voltage if the 02 sensor is disconnected? IF the O2 sensor is unplugged, should it throw a code? Thanks in advance

GA_TMAC

Yes, it should report 0.470volts with O2 sensor disconnected. This is the bias voltage that ECM provides on the purple wire. O2 sensor will swing between 0.2 to 0.9 volts under normal operating conditions. Code 44 and 45 are lean - rich condition codes if O2 sensor is fully operational.

//RF