Oxygen sensors

JTOMRAI1

MEMBER
2007 CHRYSLER ASPEN
110,780 MILES

I replaced my rack and pinion in January 2013. Since then the check engine light has stayed on. I received code P0032 and was told to replace my upstream O2 sensors. I did this. The light stayed on. I took it to a garage and they checked things out and said I needed to change my plugs, ignition coils, and downstream O2 sensors. I did this also, except for the down stream sensors. My CEL still comes on and says code P0032. I know the upstream sensors are before the catalytic converter, and the downstream sensors are after, but I can't find my catalytic converter on this vehicle. I only found two O2 sensors, also. Not the 4 that all the computers say it should have. Any ideas? Thank you.

2 Replies

CARADIODOC

MECHANIC
33,738 POSTS

I can't find a reference to code 32 in my older service manuals but I do have 13 codes related to the various oxygen sensor heater circuits between codes 30 and 58 so logic dictates code 32 is the same. Fault codes never say to replace parts. They only indicate the circuit or system that needs further diagnosis. In this case since we know the problem is likely related to the rack and pinion service I'd be looking for a cut or pinched wire long before I'd think about replacing a sensor. Also check the terminals in the electrical connectors for signs of corrosion. If a connector had to be unplugged during the rack replacement also check if a terminal got stretched or pushed out when the plug was reconnected. That's the first thing listed in every troubleshooting chart in the service manuals but I've only actually found that once. That occurs when the plug is pulled apart and reconnected and the terminals don't mesh properly.

I'm sorry I can't tell you which sensor this code relates to. If you have a four cylinder engine you will only have one upstream and one downstream sensor. V-6 and V-8 engines usually have one of each on each side of the engine for a total of four but sometimes the two sides of the exhaust will come together in a Y-pipe, then there will be a single downstream sensor. In particular Ford often does that to save a few bucks but it makes diagnosis more difficult. You have a V-8 engine so there should be four sensors.

If a visual inspection doesn't reveal the cause of the problem you will need a scanner that displays live data so you can watch what the sensors are doing. Oxygen sensors don't work until they are up to around 600 degrees. The internal heaters are used to get them there much faster after starting a cold engine and to keep them there during prolonged idling. Watch the sensors begin to switch between "rich" and "lean" a couple of times per second. They used to be required to do that within three minutes of starting the engine but with the heaters you can expect to see that within less than a minute. Watch for one sensor that doesn't start switching when the others do.

Next, once the suspect sensor has been identified you can do a continuity test on the heater circuit to locate the short or break in the wire. You will have to have a copy of the manufacturer's service manual or DVD to find the wire colors, then I can help with interpreting the test results.