V40/V70 Oxygen sensors

I have a V70 AWD (1997) converted to LPG and have minor problem with O2 sensor.

Haynes manual only shows 1 O2 sensor for the range of vehicles, but the AWD is different it definitly has 2.
Looking at the tech info for the clever bits of the conversion, it shows as an alternative the V40 wiring diagram with 2 O2 sensors.
Could any of your members confirm whether all the V40 or some of them have 2
Do any other V70 models have 2?

Your help appreciated.

iM NOT REPLYING TO YOUR QUESTION, HOWEVER I OWN A V40 1.8 SE (1997) AND AM ABOUT TO CONVERT IT TO LPG ON TUESDAY, CAN YOU TELL ME HOW YOUR VOLVO RUNS. I PREVIOUSLY HAD A VAUXHALL VECTRA CONVERTED TO LPG BUT THIS HAD A FEW RUNNING PROBLEMS DUE THE BACK FIRING AND BLOWING THE AIR FILTER HOUSING COMPLETELY OFF.

ANY HELP, I WOULD APPRECIATE

RGDS

Nathan
V40 1.8SE owner

[Multiplex]

Hello

Two heated oxygen sensors (HO2S) are used with the Motronic 4.4 engine management system fitted to your V70AWD. The reason the second sensor is used is to monitor the condition of the catalytic converter. The front sensor sends data back to the engine management system about the oxygen content in the exhaust and from this the engine management system can vary the air to fuel ratio. Early non-turbo V70s fitted with the fenix engine management system only had one oxygen sensor. The same goes for the S/V40s - Early fenix systems only had 1 sensor and later EMS2000 systems have 2 sensors.

Chris.

Hi Chris,

You seem up on EMS so may I ask ask you wether the second O2 sensor (behind the cat)on a V40 is used for monitoring & alarm purposes only or does it participate in controlling FA ratio etc..?

Rgds
Amsterdam

[Multiplex]

Hello

Two heated oxygen sensors (HO2S) are used in the EMS2000 system. The heated oxygen sensors (HO2S) are checked as usual for short-circuits and open-circuits. If either of these faults occurs, diagnostic trouble code (DTC) EFI-212 (front heated oxygen sensor (HO2S)) or EFI-153 (rear heated oxygen sensor (HO2S)) are stored. In addition, the signal from the front heated oxygen sensor (HO2S) is checked. This check is carried out as follows: The engine control module (ECM) receives exhaust composition data from the front heated oxygen sensor (HO2S). Using this information the engine control module (ECM) calculates injection period. Because the front heated oxygen sensor (HO2S) is located upstream of the three-way catalytic converter (TWC) it is subject to attack by the uncleaned exhaust gases. This leads to the sensor aging and its signal changing

These changes are monitored by checking:
-front heated oxygen sensor (HO2S) mean signal voltage
-rear heated oxygen sensor (HO2S) control
-front heated oxygen sensor (HO2S) period.

To determine front heated oxygen sensor (HO2S) mean voltage the engine control module (ECM) uses the rear heated oxygen sensor (HO2S) signal. This signal provides information about the exhaust gas oxygen composition downstream of the catalytic converter. The engine control module (ECM) can use this information to take account of front sensor aging in its injection period computations.

The mean rear sensor signal voltage should be approximately 1.35 V when twin heated oxygen sensor (HO2S) control is active. First injection period is calculated on the basis of the front heated oxygen sensor (HO2S) signal, then the rear heated oxygen sensor (HO2S) mean voltage is checked. If this is not 1.35 V then injection period calculations are adjusted to achieve the correct mean voltage for the rear heated oxygen sensor (HO2S).

A defective sensor may also have the correct mean signal voltage. For this reason the front sensor response time is also monitored. The engine control module (ECM) monitors how long it takes for the front heated oxygen sensor (HO2S) to switch from lean to rich to lean again. When the response time becomes too long for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-435 Front heated oxygen sensor (HO2S), is stored.

The rear heated oxygen sensor (HO2S) response time is also checked. Fuel trim is carried out in a controlled cycle and if a signal from the rear heated oxygen sensor (HO2S) is not received within a set time diagnostic trouble code (DTC) EFI-153 Rear heated oxygen sensor (HO2S) is stored.

Twin heated oxygen sensor (HO2S) control starts and remains active when:
-the front heated oxygen sensor (HO2S) has started control
-the rear heated oxygen sensor (HO2S) has reached operating temperature
-engine coolant temperature (ECT) exceeds 60°C
-mass air flow is between 110 and 800 mg/tdc
-engine speed is between 1,150 rpm and 4,000 rpm.

Twin heated oxygen sensor (HO2S) control is suspended during fuel shut-off, if the engine control module (ECM) detects misfiring (diagnostic trouble codes (DTCs) EFI-543, 545) or if the engine control module (ECM) detects a fault in:
-three-way catalytic converter (TWC) (diagnostic trouble code (DTC) EFI-443)
-heated oxygen sensor (HO2S) preheating (diagnostic trouble code (DTC) EFI-521 or EFI-522)
-mass air flow (MAF) sensor (diagnostic trouble code (DTC) EFI-121)
-engine coolant temperature (ECT) sensor (diagnostic trouble code (DTC) EFI-123).

Catalytic converter diagnostic

The three-way catalytic converter (TWC) stores oxygen found in the exhaust gases and uses it to make toxic gases less dangerous. The catalytic converter is a three-way catalytic converter (TWC) in which HC (hydrocarbons) and CO (carbon monoxide) are oxidized and NOx (oxides of nitrogen) are reduced. As the three-way catalytic converter (TWC) ages its ability to store oxygen drops. This reduces the conversion capacity of the three-way catalytic converter (TWC). To avoid dangerous emissions the engine control module (ECM) checks three-way catalytic converter (TWC) efficiency. This check is carried out as follows.

Two heated oxygen sensors (HO2S) are used to check the three-way catalytic converter (TWC) one upstream and one downstream of the catalytic converter. To determine catalytic converter efficiency the amplitude of the heated oxygen sensor (HO2S) signals is compared. During the catalytic converter diagnostic a controlled lean/rich fuel/air mixture cycle is carried out. When three-way catalytic converter (TWC) efficiency is good and the fuel/air mixture is normal, the front heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude) while the rear heated oxygen sensor (HO2S) signal is even (small amplitude).

When three-way catalytic converter (TWC) efficiency is poor and the fuel/air mixture is normal, the rear heated oxygen sensor (HO2S) signal switches between rich and lean (large amplitude). When this amplitude exceeds a certain limit for a number of diagnostic tests, diagnostic trouble code (DTC) EFI-443, Three-way catalytic converter (TWC) efficiency, is stored.


Chris

Gobsmacked!!!!

I take it you have access to EMS2000
system manuals on CDrom??

Seems the rear O2 sensor is performing more than just
a monitoring function and it's data is actually used to
calibrate the front sensor.

Oh well - thats the straight throu pipe idea blown away!!


Thanks Chris - much appreciated, BTW do work for Volvo or Bosch?

Rgds
Amsterdam