P0155     Engine primary oxygen sensor heater circuit problem

On late 90s imports, you will see this P0155 especially if you have primary and secondary oxgen sensors. The primary oxygen sensors sit at the engine exhaust manifolds whereas the secondary sits at the back of the catalytic converter underneath the vehicle. In this set up, the primary sensors are used to monitor the engine performance and the secondary sensor is used to monitor the catalytic converter. In this code, one of the primary oxygen sensor is at fault and the way to check this is to monitor the voltage signal from the sensor signal wire if they are switching. You can also manually enrich the fuel mixture or make it lean by introducing fuel vapor (use propane gas to do this) in the engine vacuum line. When enriched, the voltage reading should go up around 0.9 v, like wise if you introduce a vacuum leak to make the mixture lean, the voltage reading should go down near zero.

If your oxygen sensor has 4 wires on it, it only means it has a heater circuit on it and it is used by the sensor to make the sensor more responsive to the demands of the engine. The heater usually is a separate circuit of wires that are use to supply power and ground to the heater element inside the sensor. To fix this code is normally done by replacing the sensor if they are more than 50,000 miles old (for older engines) and 100,000 miles for newer engines. If the signal wire does not switch, check the continuity of the signal wire from the sensor to your computer. ATS can supply you a detailed check up for the oxygen sensor for most automotive vehicles until 2005 models.

NOTE: If you do not have an obd2 scanner or code reader, you can get the obd2 codes (for vehicles made after 1996 to present) by seeing your nearest automotive parts stores like PEP Boys, Auto Zones, Auto Value, Bumper to Bumper, etc...and they usually give FREE code scanning to promote their parts.

CODE     Meaning or Description

P2327 Engine Ign Coil Control Ckt
P2328 Engine Ign Coil Control Ckt
P2329 Engine Ign Coil Control Ckt
P2330 Engine Ign Coil Control Ckt
P2331 Engine Ign Coil Control Ckt
P2332 Engine Ign Coil Control Ckt
P2333 Engine Ign Coil Control Ckt
P2334 Engine Ign Coil Control Ckt
P2335 Engine Ign Coil Control Ckt
P2336 Engine Cyl #1 Knock sensor
P2337 Engine Cyl #2 Knock sensor
P2338 Engine Cyl #3 Knock sensor
P2339 Engine Cyl #4 Knock sensor
P2340 Engine Cyl #5 Knock sensor
P2341 Engine Cyl #6 Knock sensor
P2342 Engine Cyl #7 Knock sensor
P2343 Engine Cyl #8 Knock sensor
P2344 Engine Cyl #9 Knock sensor
P2345 Engine Cyl #10 Knock sensor
P2346 Engine Cyl #11 Knock sensor
P2347 Engine Cyl #12 Knock sensor
P2400 Engine Evap Emission Pump Control Ckt
P2401 Engine Evap Emission Pump Control Ckt
P2402 Engine Evap Emission Pump Control Ckt
P2403 Engine Evap Emission Pump Control Ckt
P2404 Engine Evap Emission Pump Control Ckt
P2405 Engine Evap Emission Pump Control Ckt
P2406 Engine Evap Emission Pump Control Ckt
P2407 Engine Tank Fuel Cap Sensor Ckt
P2409 Engine Tank Fuel Cap Sensor Ckt
P240A Engine Evap Emission Leak Pump Heater Ckt
P240B Engine Evap Emission Leak Pump Heater Ckt
P240C Engine Evap Emission Leak Pump Heater Ckt
P2410 Engine Tank Fuel Cap Sensor
P2411 Engine Tank Fuel Cap Sensor
P2412 Engine Tank Fuel Cap Sensor
P2413 Engine EGR Performance
P2414 Engine Oxygen Sensor Exh sample
P2415 Engine Oxygen Sensor Exh sample
P2416 Engine Oxygen Sensor Exh sample
P2417 Engine Oxygen Sensor Exh sample
P2418 Engine Evap Emission Valve Control Ckt
P2419 Engine Evap Emission Valve Control Ckt
P2420 Engine Evap Emission Valve Control Ckt
P2421 Engine Evap Emission Control Valve
P2422 Engine Evap Emission Control Valve
P2423 Engine Emission HC Efficiency
P2424 Engine Emission HC Efficiency
P2425 Engine EGR Coolant Valve Cntl Ckt
P2426 Engine EGR Coolant Valve Cntl Ckt
P2427 Engine EGR Coolant Valve Cntl Ckt
P2428 Engine Engine Exh Gas Temp
P2429 Engine Exh Gas Temp
P242A Engine Exh Gas Temp
P242B Engine Exh Gas Temp
P242C Engine Exh Gas Temp
P242D Engine Exh Gas Temp
P242E Engine Exh Gas Temp
P242F Engine Diesel Particulate

The above list is still being updated, please come back later to see the rest or contact ATS if you don't find your obd2 code

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