Where are the o2 sensors on a Ford Freestar located and their designations?

Answer 1

Here is the low-down on oxygen sensors, and their location designations explained:

Oxygen sensors are screwed into the exhaust system at various points. Some people say that there are 4 oxygen sensors, but technically, that is not correct. Only the front 2 are considered oxygen sensors.

These oxygen sensors are screwed into the exhaust pipe or directly into the exhaust manifold, one on each bank. Because they are in front of the catalytic converter, this is often referred to as 'upstream'.

The other 2 are actually called catalyst monitors. They are oxygen sensors, but they serve a different purpose. They monitor the activities of the catalytic converters, thus the name, catalyst monitors. They are screwed into the exhaust one on each bank, after, or downstream, of the catalytic converters.

The location names for them are as follows:

On a V6 or V8 engine:

• • the passenger side bank on a forward facing engine, or the bank closest to the firewall on a transverse mounted engine, is bank number 1, so the forward / upstream sensor on that bank would be "bank 1, sensor 1."
  • The driver's side bank (forward facing mount engine), or front bank (transverse engine) would be bank number 2, thus the forward / upstream sensor on that bank would be "bank 2, sensor 1," and the rearmost / downstream sensor on that bank would be "bank 2, sensor 2."

REMOVE TIP: you may have to bend part of the transmission heat shield out of the way - be sure to put it back when done.

NOTES:

• Use lots of penetrating oil - allow to soak - to make removal easier and avoid damaging the exhaust pipe
• the sensors are screwed directly into the pipe at a 90 degree angle and look like spark plugs with either 8", 12", or 14" wires attached to them
• Tools:
• ** ** it is usually a 7/8ths size wrench
  • special-purpose oxygen sensor socket - not expensive, and commonly offered for free use by the auto parts store
• Inspect the condition of wires and that they are not touching any parts of the exhaust system
• Before getting under the van, make sure to disconnect the battery if you have the Air leveling suspension

Rule of thumb: Bank 1 is on the side of the engine with cylinder #1

6 Cylinder numbering:

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1 2 3

4 5 6

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Front of vehicle

- EditorialAnd before spending any $$ on replacing a sensor, I would test it to ensure it really really has failed! It's very likely someone read the DTC (diagnostic trouble codes) that cited an oxygen sensor reading - but then said something that leads you to believe it's a failed/bad sensor and needs replacing. The vast majority of times that is NOT the problem.

Take those codes and research them on the internet! (see "Related Links")

A perfect example are P0171 and P0174 codes - indicate a lean mixture was read in bank 1 & 2 (respectively). On the Windstar, that's a prime symptom covered in Technical Service Bulletin TSB# 03-16-1 (see "Related Questions")

The auto parts store guy had me ready to spend $80 on 2 sensors. - CCoach