Lamdasond Light is On

[Guest]

Hello

I'm new to this group as I have only had my gold 740 wagon for 6 months and is running relatively well.

About 2 months ago the lamdasond light came on, at the dash and the on board diagnostic unit confirms there's something wrong with oxygen sensing. During a routine service (170k) my mechanic put his own 02 sensor on to it and confirmed that there is a signal coming from the 02 sensor on the catalytic converter but the car is still running rich (not so bad at idle). This would explain the heavy fuel bills lately. It seams the car's computer is not responding to the 02 sensor and adjusting the mixture properly.

I could leave it with him but he is no expert in this area and it would take him some time to figure it out. Can anyone offer any suggestions?

Thanks

George Vrionis

[George Vrionis]

Just as an update to this problem the diagnostic codes read are:

2-2-1 (Adaptive Lamda control lean part load)
1-2-3 (No signal from coolant temperature sensor or short to ground. Engine behaves as though hot)
2-3-1 (Adaptive Lamda control lean or rich part load)

Where is the coolant temperture sensor? Is it attached to the radiator?

Hope someone can help.

Cheers

[George Vrionis]

For those interested, I had the O2 sensor replaced and the lamdasond light went out.

[George Vrionis]

Its back, confound it.

The light is back on so I have been asked to take it back in to the mechanic's. I'll let you all know what they say this time.

Still, any suggestions would be welcome.


Cheers

George Vrionis

[George Vrionis]

The mechanic said now there is nothing wrong with the oxygen sensor, its the coolant level temperature sensor which is either faulty or the wire is grounding somewhere. He said he would have to do a more extensive search to find the problem.

Before I give this guy a blank, signed cheque, can anyone offer any suggestions?

I'm also having problems identifying this under the bonet. It looks like there might be two of them. Is this correct?

Cheers

George Vrionis

[matthew1]

Sorry George, I wish I could help. I just know stuff about my 850. Did you buy a Haynes or Chilton's manual for it? That may offer some help with the location of the sensor.

[George Vrionis]

Hi Matthew and all

I have the Haynes manual and have identified the sensor. I have run the initial tests according to the manual and found that the sensor does seem to be working (temp gauge works) but may not be reading accurately.

I did some checks with the multimeter and couldn't find any earthing of the cables. I even traced the wires back to the first junction box and checked all its connections and seamed OK.

Next I'll disconnect the sensor and place it in hot water with a thermometer and measure the resistance values, as per the manual. If this doesn't work I'll take it in to the mechanic.

Cheers

George Vrionis
Sydney, Australia

[George Vrionis]

Hi All

Just to let you know I solved the problem and hopefully someone else may benefit.

The two vacuum hoses protruding from the end of the air intake (engine side) were affected. If you trace them back they end up past the air intake filter box (underneath on the frame) and then connect to a black cylinder on the front left hand side. The fat hose was squished under a solid tube and the small hose was disconnected at the black cylinder. Fixing these fixed the problem and now the lamdasond light is extinguished and the fault code on the diagnostic computer is 1-1-1 meaning all is well.

Beep Beep

George Vrionis
Sydney Australia

[George Vrionis]

I can't believe it. Its Back! That stupid lamdasond light is back on!

A week after thinking I'd fixed it, its back on again.

I have discovered that if you disconnect the battery, the computer resets itself to such an extent that it takes about a week for this fault/light to come up!.

This makes sense as when I bought the car a year ago, the battery was cactus and they had to replace it (with a crappy one mind you). When the so called experts changed the oxygen sensor, they had disconnected the battery. ( I know this as I had to put the code back into the radio). I didn't think you needed to disconnect the battery to install an oxygen sensor into the catalytic convertor. ( I could be wrong)

Now I change batteries and think the light has gone out because I found those disconnected vacuum hoses.

Beware! If you buy one of these cars and the battery has just been changed certain faults may not show up until after a week!.

So now I'm going to bite the bullet and take it into a dedicated Volvo service centre. I'll instruct them not to disconnect the battery and I'll even put wax onthe bastard's terminals!.

I"ll let you know how they go.

Regards

George Vrionis
Sydney, Australia

[George Vrionis]

Finally fixed. The temperature sender was replaced by an authorised Volvo dealer and the light has gone out. It has been two weeks and it is still out.

So let me summarise:

If your Lamdasond light is on (1991, 740 especially), check the following:

Oxygen Sensor on (Catalytic Converter)
Vacuum Hoses
Temperature Sender
Possibly air flow mass meter

If you have a diagnostic computer believe what it says.

If the battery is disconnected it will clear the faults within the diagnostic computer for up to a week before they re-appear. So be warned, when you buy one of these cars that has a dead or new battery, there may be problems hidden until the computer picks them up again (a few days later after you have departed with your cash). If you take it in to get fixed and it is returned with the battery having been disconnected (then connected) be wary, the light may come on again in a week. The repair people probably know this trick and use it as a smoke screen to make it look like they