Chevy Express Oxygen Senor Codes P0140 P0160

Question:
I had two repair shops to charge me for a check engine light that have cost me over $4000.00 and the check engine light is still on. Both oxygen sensors was replaced and there is no activity detected on bank 1 and 2 sensors. They said that the sensors was bad. Both sensors was new and cost me $179.00. The other shop replaced the distributor cap and rotor, spider fuel injector assembly and distributor assembly.

He said fuel pressure regulator injector leaking causing misfire. He changed my master cylinder, power steering pump and steering gear. This was other work that i let him do for me. Now a brake light and a flashing ABS light on that was not on before. Now mechanic tells me the computer (PCM) is bad and he wants $2100.00 to replace it.

Answer:
An ABS lght on could just be a bad wheel speed sensor. I would need to the stored trouble codes to help with that problem.

For the check engine light and O2 sensor problem on you Chevy Express cargo van we would also need to know exactly what codes are stored. The oxygen sensors create their own voltage signal when they reach approximately 600 degrees F and send that signal to the PCM. The voltage fluctuates from 0 - 1 volt. A sensor that is not working will show a steady .5 volts while looking at live data on a diagnostic computer.

A bad PCM is not very common for oxygen sensor codes. Normally the problem is in the heating circuit not sending voltage to them to get them hot quicker so when people look at the data they see no fluctuation and make the wrong diagnosis. Or, the sensor itself is bad, but you already had them replaced.

The continuity of the wires back to the PCM would need to be checked to make sure this is not a wiring problem. Electrical testing is needed to confirm this. Do you know if that was done?

A possible problem is that the catalytic converters are at fault. This will give codes, lack of power or even engine misfire. This can be caued by the engine running bad for a long time, age or even bad fuel.

With the spider fuel inector assembly being replaced for a leaking pressure regulator, it is possible that if your Express Van was running rich like that for an extended period of time that could have caused the catalytic converter(s) to fail. This is a common cause. An engine running rich will dump raw fuel into the exhaust and converter and cause the converter to fail. This can give false readings on oxygen sensors, check engine light or cause them to go bad.

Without you giving us the actual codes and sensor readings we cannot give a better diagnosis.

VISITOR:
For the answers to your question: I had the van checked this morning and this is what came up PO300 random misfire detected, PO140 02 sensor circuit no activity detected (bank 1 sensor 2, PO160 02 sensor circuit no activity detected (bank 2 sensor 2). NO code came up for the ABS flashing light but the red light on the left side that come on with brake on it. Last year i replace both catalytic converters. The engine have not ran bad or miss or shake and it run very good. Two weeks ago i had new plugs and wires install. About 1 1/2 years ago i had the spider injector assembly distributor assembly and injectors replaced.

Answer:
Both these codes are post converters and are saying that either the sensors circuit are faulty because of no activity or there IS ACTUALLY no or low activity because the catalytic converters are not cleaning the exhaust efficiently.

• Test the purple wire at each sensor for power, this is the heater circuit. If no power then check all your fuses.
• Test continuity of each sensor connector wires back to the PCM.
• Have the MAF tested because if the MAF readings are innacurate (skewed) then O2 sensor readings cannot be calculated properly. MAF may just need the sensing resistors inside cleaned with brake cleaner.
• Inexpensive converters will not clean the exhaust effieciently and cause these codes as well.