Contour Enthusiasts Group Archives Forums Modifications Duratec Maintenance Multiple Queries!

I put fuel injector cleaner (thanks Tony2005) in my car and it has seemed to fix the lack of power problem. I bought a OBD II reader and it brings up codes 0155 and 1151 do both theses sensors need to be replaced and where exactly are they located on the car. Thanks again for all your help.
Mike

Those codes are for the oxygen sensor heaters. Especially the 0155 is more likely to be a wiring problem or heaven forbid, a processor problem.

Reset computer, if it comes again, check the common causes for both codes and start troubleshooting from those. Good luck. It could be something as simple as water in the harness connector (this can happen if you have been driving in the pouring rain and water drips on the connector).

From TSB.
P0155 - Bank 2 (Radiator side) Upper HO2S Sensor Heater Circuit Malfunction (HO2S-21)
During testing, the HO2S heaters are checked for opens/shorts and excessive current draw. The code will set when current draw exceeds a maximum calibrated limit or falls below a minimum calibrated limit and/or an open or short is detected.

�· Blown fuse
�· Short to VPWR in harness or HO2S
�· Water in harness connector
�· Open VPWR or GND circuit
�· Low battery voltage
�· Poor electrical connections from PCM to HO2S sensor
�· HO2S heater
�· PCM

P1151 - Lack of HO2S-21 (radiator side upper sensor) Switch, Indicates Lean
When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time. Electrical:
�· Short to VPWR or VREF in harness or HO2S
�· HO2S circuit shorted to Ground
�· Water in harness connector
�· Open circuit
�· Corrosion or poor mating terminals and wiring
�· Damaged HO2S
�· Damaged PCM (other DTCs should be present)
Fuel System:
�· Excessive fuel pressure (stuck fuel pressure regulator, restricted fuel return lines, etc.)
�· Leaking/contaminated fuel injectors or fuel pressure regulator
�· Low fuel pressure or running out of fuel (fuel pump concern, fuel supply line restrictions, low fuel level, etc.)
�· Vapor recovery system (stuck VMV, etc.)
Induction System:
�· MAF contamination
�· Air leaks between MAF and throttle plate
�· PCV system / Other vacuum leaks
�· Improperly seated engine oil dipstick
EGR System:
�· Leaking gasket
�· Stuck EGR valve / Leaking diaphragm or EVR
Base Engine:
�· Oil overfill
�· Incorrect cylinder compression
�· Exhaust leaks before or near the HO2S
�· Secondary air stuck on

Bank 2 (Radiator side) Upper HO2S Sensor Heater Circuit Malfunction (HO2S-21)
To the left of the red arrow in this picture is the O2 sensor in question. On this 2-D image, the sensor is partially hidden by the front "frame". Note you might have to remove the front radiator deflector to get to it. 22 mm crescent wrench (or 7/8 inch) or a O2 sensor removal tool ($10 at Advance or Autozone).

Originally posted by chongo:

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The easy things to do are to check for
�· Blown fuse in the fuse box.
�· Check for broken or chafed wiring from the sensor to the connector (probably blue or green color connector) and connector to PCM (under the Power Steering Reservoir at the passenger side strut)
�· If there appears to be water in harness connector, use hair dryer to dry it, spray some WD-40, wipe it dry, reconnect and then tape over with duct tape (to prevent water from getting to it)
�· Also check to make sure PCM connector is not loose or wet.
. You may actually just want to put in a new O2 sensor. (about $70) but if you want to test that is fine too.
First Test
1) Disconnect the 02, but leave the battery connected
2) Measure the resistence between the PWR and GRND terminals of the sensor. it should be approx 6 ohms at 68 degrees F.

Second Test
1) With the sensor connected and the engine running, measure the voltage between the H02S and SIG RTN (Ground) of the 02 sensor. voltage should fluctuate between 0.01-1.1 volts.

If the first test doesn't read around 6 ohms, or if the second test yeilds slow fluctuation or voltage isn't within specification, replace the sensor.