“ We constantly receive Ford hotline calls about repeating oxygen (O2) sensor codes. Often, the technician has replaced the O2 sensor, sometimes more than once, only to have the code return. Most of these calls revolve around identifying the location of the O2 sensor by the code. ”

We constantly receive Ford hotline calls about repeating oxygen (O2) sensor codes. Often, the technician has replaced the O2 sensor, sometimes more than once, only to have the code return. Most of these calls revolve around identifying the location of the O2 sensor by the code.

All OBD-II Ford 4-cylinder engines have two sensors: 1-1 and 1-2. On V engines, there are two, three or four sensors: 1-1, 2-1, 1-2 and on some with dual exhaust, 2-2. The first digit in the number is the Bank ID. 1 = Bank 1, 2 = Bank 2. The second digit is its Location ID. 1 = close to the exhaust manifold, 2 = behind the CAT.

On all OBD-II Ford engines, Bank 1 is where cylinder No. 1 is located. On rear-wheel drive, this is the passenger side of the vehicle, and on front-wheel drive, it is the bulkhead (firewall) side of the engine. The driver's side or radiator side of the engine is Bank 2. So if you get a code for 2-1 on a V-8 pickup, that would be located on the driver's side front sensor. A code for 2-2 on a V-6 or V-8 Ford Taurus would be the back sensor for the radiator side of the engine. Make sense?

A typical complaint is that the code is set for a lean O2 sensor. On some OBD-II vehicles and scanners there may be up to eight codes for each O2 sensor so it is important to know the code number and what test was being run when the code was found. With a code P0141 for a heater circuit fault, found in the key on engine off test (KOEO), you should be able to go right to the sensor and perform tests to find the problem. But a code P0141 in memory only is an intermittent problem that isn't there right now, so most tests that could be performed will not find the problem.

When dealing with Ford vehicles, perform OEM or manufacturer-specific KOEO, KOER and memory tests and record the code numbers where they are found.

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