Question: 2004 Ford Taurus SES
Hello: I enjoy your column and newsletter.
I'm having an issue with a 2004 Ford Taurus SES, 12 Valve engine (U) with 52,000 miles. Engine light came on in March, took to AutoZone, code for Ox sensor bank one and replaced. Was fine for 3,000 miles. Now light comes on occasionally and new code is P2196. Ford has a TSB number 17692, "Rich Condition". Could another O2 sensor have gone bad? Should I look for a short? Prefer not to pay the dealer to "diagnose", but don't mind a "repair".
Thank you,
Dan Eudene
Answer:
Well Dan, if you are looking to me to diagnose the problem for you, I can't. Without having the car here for me to perform tests, the best I can do is offer suggestions on how to find the problem and the most likely causes.
DTC P2196 - Lack of HO2S-11 Switch, Sensor Indicates Rich. If you read the code carefully, you will see it does not indicate a bad HO2S-11, but rather the sensor is telling us it has sensed a rich fuel mixture. So you can change the HO2S-11 all day, and it will not fix anything. An HO2S indicating rich at the end of a test is trying to correct for an over-lean condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.
So the HO2S-11 is working perfectly and is actually telling you the mixture is too rich. So what we need to do is address the rich fuel mixture problem. There can be a number of causes for this condition. The first thing I would check is the PCM wiring harness where it rests on the bracket at the right side front strut turret. Look at the underside of the harness (a mirror will help the inspection) and check for possible chafing on the cross car beam. If there are damaged wires, repair them as required. If it is a shielded wire that is damaged, you will need to replace the whole wiring harness. A shielded wire can not be repaired.
If the harness is okay, then we need to look at other possibilities. Some of these are:
Electrical:
- Short to VPWR in the harness or H)2S
- Water in the harness connector
- Open or shorted HO2S circuit
- Corrosion or poor mating terminal contacts or wiring
- Damaged HO2S
- Damaged PCM
Fuel System
- Excessive fuel pressure
- Leaking or dirty fuel injectors
- Leaking fuel pressure regulator
- Low fuel pressure or running out of fuel
- Vapor recovery system
Induction System
- Air leaks after the MAF
- Vacuum leaks
- PCV system
- Improperly seated dipstick or oil fill cap
EGR System
- Leaking EGR gasket
- Stuck EGR valve
- Leaking diaphragm or EVR
Base Engine
- Oil overfilled
- Cam timing
- Cylinder compression
- Exhaust leaks before or near the HO2S(s)
Check out these possibilities and I'm sure you will find the cause of the rich condition, but my money is on a damaged wiring harness.
