I have a 95 benz s320. I changed the o2 sensor and the mass airflow sensor like two months ago and the check engine keep on coming on like crazy, giving me the same code p0132 and p1136. I know the o2 sensor can lead me to get code p1136, so i thought maybe the o2 sensor that i put in the car was maybe defective, so i ordered a new bosh o2 sensors direct fit from Authoausaz the one before the catalytic and after the catalytic i installed it yesterday reset the codes and drive the car for a few and here we go again with the same code p0132 and p1136 keep resetting it and it keeps coming back, my car burn alot gas only give me 300 miles on a full tank. I know p0132 is the o2 sensor before the cat i replaced it reset it and still getting the same code.

I would check the sensors heater wiring for continuity and shorting.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I Check them and they are in good shape. I had partially rewire the mass airflow sensor connecter i was wondering if that could cause that problem because i am keep on getting codes p0132 and p1131 i recently replaced the cat with a magaflow cat and i am still getting p0132 and p1131 strange my gas mileage is horrible

What did you do and why? Are you able to know if you did it right?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I partially rewired the mass airflow sensor connector because the heat melt the insulation and they were touching together, and i am pretty sure that i rewired it correctly, i am trying to think why am i keep on getting the p0132 and p1131 because i replaces both 02 sensor with oem parts and mass sensor and catalytic converter magaflow. and still getting those codes. I am getting horrible gas mileage.

Well, I am in electronics, and there is a difference between sure and pretty sure.

Was 1995 the year with the decomposing wire harnesses?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Yes, but i recently intall a new engine wiring harness in the car.The insulation of the mass airflow only melt around the engine compartment and i had rewired it from there to where the insulation were burn. And it's not the mass airflow that is giving me the check engine light. it's the 02 sensor before the catalytic converter that keep on giving me code p0132 and p1131 and here is a link they give me to do the measurement, but seem complicated don't really know how to start http://www.startekinfo.com/manual/volumes/e3/8_6/m11.jsp

Well, I'll answer here instead of at benzworld, since you've explained better here...

Giving the P0132 is a token of that the voltage on the sensor is permanently
high. High voltage, indicates a rich running engine. Changing out the sensor
will not mend that. Its merely showing what its happening. That fits your horrible gas
milage also. And since you know what you did when this occurred, rewire the MAF, well
that would be prime suspect... The MAF might give slightly off reading, at least
not wildly wrong, that would give a rich condition, that is the O2 sensor task
to discover. Your O2 may now be so full of carbon, that the other condition P1131
turns up.

Read about sensor here;
http://www.gnttype.org/techarea/ecmsensors/O2sensors.html

Other things it could be, wrong timing, leaky fuel pressure regulator.

br,
syljua

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1998 CL500 W140
1984 230E W123

Probably worth checking the coolant temp sensor as well.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Thanks for all those great info syljua. A benz tech once told me rewired the mass sensor could will give slightly off reading to the ecu, i tried to rewired it because it cost like $300 a benz tech said. I thought it was the cat and i put a magaflow cat my car have 173000 my cat look like it was clogged because i cant see thru the other end when i put a light, hopefully it wasn't a waste of money of putting a new cat. I think i'll start by checking for leaky fuel pressure regulator hopefully it's not wrong timing, and i guess i have to replace the mass airflow sensor harness since it didn't come with the engine wiring harness. Someone said in the post that it could be the temp sensor, but i don't need no where in the article they mention temp sensor. Thanks to all of you again guys.

Yes, but a faulty coolant sensor, thats giving the reading of a falsely cold
motor, will make the mixture richer. And thats your problem, you have
a too rich mixture, surplus of unburnt fuel, that you have to solve.

br,
syljua

__________________
1998 CL500 W140
1984 230E W123

Even if my temperature guage is working fine the sensor could be bad. If that is the case the sensor is not expensive i can buy one and hopefully that will solve my problem. The guage show me the car temperature is normal little bit over 80 sometimes 90 or 85. And yes it keeps on telling me the mixture is too rich sensor 1 bank 1. Thanks again for the reply

The coolant temp sensor is easy to test with a meter. I don't have the specs for your car, but I suspect they are the same as my '96 SL, which is 2500 ohms resistance at a coolant temp of 20 degrees C and 325 at 80. If you have a bad wire from the sensor to the computer, this could cause a high resistance reading, which would make the computer think the engine was cold and cause it to demand more fuel.

You might also think about getting a readout from a shop with a Star Diagnosis computer, which gives a lot more information than the OBD2 codes.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

No, the gauge is getting the signal from the same sensor, so if it is showing
correct value, the sensor is fine.

I support ctaylor738 suggestion about reading codes at Mercedes.

br,
syljua

__________________
1998 CL500 W140
1984 230E W123