Questions and Answers

Ford Windstar DTCs P0156 P0161 P0172 Q. I know what the code say is going wrong. What I don't know is what it means and how to fix it. Is this a repair I can do myself, or must I have a mechanic do it? Is it an expensive repair? OBD-II codes: # P0156 # P0161 # P0172

• 1996 Ford Windstar
• 3.8 liter V-6
• Automatic transmission
• 150,000 miles on van, 30,000 on its rebuilt engine
• ABS brakes
• P/S, A/C, cruise control

A. DTC P0156 indicates the output voltage of the downstream Heated Oxygen Sensor (HO2S) is less than some calibratable functional window.

The possible causes are:

1. Pinched, shorted and/or corroded wiring and pins.
2. Crossed sensor wires
3. Exhaust leaks.
4. Contaminated HO2S.
5. Bad HO2S.

DTC P0161 indicates a short to ground, open or short to VPWR in the HO2S heater circuit.

The possible causes are:

1. Short to B+ in harness or HO2S.
2. Water in the connectors.
3. Cut or pulled wiring.
4. Disconnected wiring.
5. Open VPWR circuit.
6. Low battery voltage.
7. Corroded or poorly mated terminals.
8. Bad PCM.

DTC P0172 indicates the air/fuel mixture ratio, Bank 1, is too lean. The fuel adaptive system is at the lean correction limit.

With these three DTC's, I would say that HO2S-11 is either bad, or unplugged.