Contour Enthusiasts Group Archives Forums General Troubleshooting How many O2 sensors?

I have used the search feature but I am seeing conflicting info. I have a 99 contour v6 MTX. I have a p171 system to lean bank 1 code and a p1131 Lack of HO2 switch sensor indidcates lean. are there 4 o2 sensors on these cars? 2 before the cat and 2 after the cat? I have a haynes manual but it doesn't say jack schitt about O2 sensors in detail. From what I have gathered in other posts the sensor that I need to replace is a PITA one in the rear. How easy is this to do myself or should I suck it up and have a mechanic do it?

The first O2 sensors in each bank monitor the A/F ratio for the PCM.
Bank 1 is the bank next to the firewall.

Therefore that code is pointing to the first O2 sensor on the firewall side.

Originally posted by Cappuccino911:

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I have a 99 contour v6 MTX. I have a p171 system to lean bank 1 code and a p1131 Lack of HO2 switch sensor indidcates lean. are there 4 o2 sensors on these cars? 2 before the cat and 2 after the cat?

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Yes, there are four O2 sensors. Bank 1 is closest to the firewall, Bank 2 is next to the radiator. Upstream is before the cat, downstream after the cat.

I have exactly the same problem on my '98 V6 AT.

I have:

• replaced the upstream O2 sensors
• replaced the PCV valve
• inspected the various intake piping that goes to the intake manifold (everything seemed OK)
• replaced the air cleaner
• replaced the fuel filter
• inspected the MAF (it seems fine)
• tested the EGR valve
• looked for other intake leaks

all to no avail.

I now have an EGR gasket and a throttle body gasket at the ready, but frankly I don't expect them to make any difference either ... bummer.

Originally posted by aekalman:

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I have exactly the same problem on my '98 V6 AT.

I have:

• replaced the upstream O2 sensors
• replaced the PCV valve
• inspected the various intake piping that goes to the intake manifold (everything seemed OK)
• replaced the air cleaner
• replaced the fuel filter
• inspected the MAF (it seems fine)
• tested the EGR valve
• looked for other intake leaks

all to no avail.

I now have an EGR gasket and a throttle body gasket at the ready, but frankly I don't expect them to make any difference either ... bummer.

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I have similar problems. In my humble opinion Ford engineer's and programmer's (they call themselves that) engine management system and implementation of OBDII is the root cause of many of the problems. You need (we all do) to find a Ford technician that knows the Contour's design and maufacturing deficiencies.

I think we need to make up a 25 or more critical questions test for the mechnaics who are to work our cars so we can weed out the poor ones) and find mechnaics that can diagnose the problem properly the first time.
Any takers?