recurring front O2 sensor code

t5ftw · Post by **t5ftw** » 29 Aug 2010, 21:59

I have CEL light on the dash of my '99 S70 T5 with aprox. 96,000 miles. I checked the code. It was O2 sensor code P1132. I had been seeing the code about two weeks until I replaced the sensor. It keeps coming back even after I replaced the front sensor.
Before I replaced the sensor, my code reader showed the freeze frame data as below
Fuel Sys 1 CL
Fuel Sys 2 NA
Calc Load (%) 2.7
ECT (F) 165
STFT B1 (%) -10.1
LTFT B1 (%) 12.5
Eng RPM 1280
Veh Speed (mph) 37

I replaced the front sensor with Bosch 15667 (0258007240D09) that I got from Amazon. I reset the code, drove around, and the code came back on. My code reader had the following freeze frame data
Fuel Sys1 CL
Fuel Sys2 NA
Calc Load (%) 10.1
ECT (F) 163
STFT B1(%) 0
LTFT B1 (%) 17.9
Eng RPM 2200
Veh Speed (mph) 64

I reset it and drove again. The code came back. This time the data is as below
Fuel Sys1 CL
Fuel Sys2 NA
Calc Load (%) 11.3
ECT (F) 183
STFT B1(%) -4.6
LTFT B1 (%) 14.0
Eng RPM 2360
Veh Speed (mph) 68

Any advice?
MY other symptoms and conditions are:
I have ETS light comes on and off intermittently. I cleaned the ETM but it did not fix it. But it seemed to made throttle response slightly smoother. I also tried to eliminate vacuum leaks by adding clamps here and there. I sprayed brake cleaner while engine running, but I could not hear anything obvious. I also cleaned MAF sensor using CRC MAF cleaner. I cannot see anything obviously dirty on the sensor wire. I am using K&N filter. I could not see any obvious puncture on the area around the sensor. I had my rear O2 sensor replaced 3 month ago. Spark plugs replaced three weeks ago. The O2 sensor code was there before the spark plug replacement.

Post by **JDS60R** » 29 Aug 2010, 22:08

Was the rear O2 sensor a Bosch sensor? Concern being that your long term fuel trim is off.

With the LTFT being both neg and pos dependent on the speed/load I would be looking at the MAF and doing a fuel injector test against LTFT

t5ftw · Post by **t5ftw** » 29 Aug 2010, 22:12

It looked to me like so. At least that's what my mechanic told me. He said he used OEM Bosch.

Post by **JDS60R** » 29 Aug 2010, 22:13

Do a fuel injector test and check the MAF performance

t5ftw · Post by **t5ftw** » 29 Aug 2010, 22:43

Thanks for the help. I will have to look for the procedure, but Is the digital multimeter the only thing I need?

Post by **JDS60R** » 30 Aug 2010, 03:29

You need an OBD2 scanner that can read the live data for STFT and LTFT (short and long fuel trim). By unplugging one injector at a time while running you can determine the max trim needed and see the performance of injectors individually. A leaking injector or an air leak at the injector often causes the trim to change.

LTFT is the idle to midrange. Yours is showing rich so the car is compensating for a lean conditions. Your short term is the higher load and the car is running rich so the trim goes negative. This could be from an intake leak,bad injector , bad MAF.

By testing the injectors one at a time we can see if one or more has gone lean (dirty) and the other cylinders are going rich to please the O2 sensor. The unburned fuel will trigger a code when the post cat O2 sees the condition.

You will need to reset the adaptives as well so the ecm release the fuel trims and starts new. This usually involves disconnecting the battery. Be careful to do it correctly as some cars need the key in a specific position before disconnecting.

t5ftw · Post by **t5ftw** » 30 Aug 2010, 20:59

Last time I replaced the sensor, I disconnected the battery longer than 1 hour but I did not try turning the key or stepping on the brake. So, I tried it this afternoon to reset ECU LTFT. So far 36 miles the code hasn't come back yet. Hopefully, this is just about LTFT resetting problem. We will see. I am not so sure though, because it was good for the first two days after the sensor was replaced. Then, I felt some difference in car performance and fuel efficiency. Finally, I got the code back. Another thing to note is that this morning I got another code, P0137. In fact, this code came on a couple of times since the rear sensor was replaced. I thought it was temporary thing but it basically came on once a month.

Post by **JDS60R** » 30 Aug 2010, 21:20

Stock exhaust?

Post by **jblackburn** » 30 Aug 2010, 21:46

Are you the one that lives around Blacksburg? I'm sure the code will return - if you want to stop by some time next weekend (I will be out of town this weekend), I can try to figure out what's causing it to come back. My guess, though, would be that something's letting unmetered air into the system and annoying it.

850tech · Post by **850tech** » 30 Aug 2010, 22:43

Unmetered air is a strong possibility and Anything related to the A/F metering is possible, but I also noticed you said that the rear O2 was also replaced not to long ago. If they are not of the same type/manufacturer this code can also set. The ECM compares the front and rear O2 adaption values and if the signal varries by more then 3% this DTC will set, and both the front and rear can set the same code. Also it should be noted that with the dealer tool P1132 translates into ECM-280A, which has four diffirent types of fault:

Signal too high
Signal too low
Signal Missing or,
Faulty signal

As you can see this leaves multiple avenues for diagnosis

Also, being a hard fault (consistantly returning) I would not rule out broken or shorted wiring, or poor connections as a possibility.
Live data is a must for a correct first time diagnoisis on a code like this, you need to know what your fuel trims are doing as JDS60R stated, as well as what the O2's themselves are doing, and how they react to changes in the A/F ratio.

Anyway Here's all the DTC information, if you can narrow it down to which of the four sub categories of fault your dealing with I can post the diagnostic procedure tomorow night.

ECM-280A FRONT HEATED OXYGEN SENSOR (HO2S), FAULTY SIGNAL
DIAGNOSTIC TROUBLE CODE (DTC) INFORMATION

Condition
Probe monitoring begins after probe preheating diagnostics are complete. Diagnostic Trouble Code (DTC) ECM-280A is stored if there is a fault in the front Heated Oxygen Sensor (HO2S) or its wiring causing the signal to deviate from its permitted range

The control module registers four different types of fault:

Signal too high The control module compares the front and rear adaptation values. A Diagnostic Trouble Code (DTC) is stored when the values deviate by more than 3%.

NOTE: The fault may be in the front or rear Heated Oxygen Sensor (HO2S) circuit.

Signal too low The control module monitors the aging of the probe by checking its dynamics when switching between lean and rich mixtures. The Diagnostic Trouble Code (DTC) is stored if the control module registers that the probe is operating too slowly.
Signal missing The control module monitors cross-induction from the probe preheating. Diagnostic Trouble Code (DTC) is stored when cross induction exceeds the permitted value.
Faulty signal A Diagnostic Trouble Code (DTC) stored when:
the control module registers that the signal from the front probe is above 4.8 V for too long
the signal from the front probe does not deviate from [lambda] = 1
the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.

Condition

The rear Heated Oxygen Sensor (HO2S) control is disabled
Three-way catalytic converter (TWC) diagnostic is disabled

Possible source

Signal too high:

air leakage in the exhaust system
short-circuit to power supply or ground in the signal cable (+) or supply cable for pump current
defective Heated Oxygen Sensor (HO2S)

Signal too low:

the cable for calibration current and the cable for pump current are short-circuited to each other
open-circuit in signal cable (-)
open-circuit in cable for calibration current
defective Heated Oxygen Sensor (HO2S).

Signal missing:

signal cable (+) and signal cable (-) short-circuited to each other
one of the cables for Heated Oxygen Sensor (HO2S) preheating is short-circuited to the probe's other wiring
defective Heated Oxygen Sensor (HO2S).

Faulty signal:

short-circuit to supply voltage or ground in signal cable (+)
short-circuit to supply voltage or ground in signal cable (-)
short-circuit to supply voltage or ground in pump current cable
short-circuit to supply voltage or ground in calibration current cable
open-circuit in signal cable (+)
defective Heated Oxygen Sensor (HO2S).

Condition

Malfunction Indicator Lamp (MIL) lit.