I have a 1997 sport and I received a check eng light last night. I have only 28,900 miles on my jeep. Well when I got home I did the self diagnostic by turning the key on/off/on/off and finaly back to the on postion. It displayed the fault code 12 and the code 21 before it gave me the code 55 telling me all codes where displayed. From what I can tell the code 12 is battery power to PCM was disconnected. The code 21 has several options to what it could be :
1) Oxygen sensor input voltage maintained above the normal operating range.
2) Oxygen sensor response slower than minimus required switching frequency. or upstream oxygen sensor heating element circuit malfunction.
3) o2 sensor voltage too low, tested after cold start. / 02 sensor voltage to low, tested after cold start
4. a slow switching oxygen sensor has been detected in bank 1/1 during catalyst moniter test.
my question is how can I tell what one it is the true fault and I need to replace to fix it.
thanks,
MtHunter
1) Oxygen sensor input voltage maintained above the normal operating range.
2) Oxygen sensor response slower than minimus required switching frequency. or upstream oxygen sensor heating element circuit malfunction.
3) o2 sensor voltage too low, tested after cold start. / 02 sensor voltage to low, tested after cold start
4. a slow switching oxygen sensor has been detected in bank 1/1 during catalyst moniter test.
my question is how can I tell what one it is the true fault and I need to replace to fix it.
thanks,
MtHunter
