'99 V70 2.4 NA - O2 sensors battle

Post by **abscate** » 19 Mar 2020, 10:07

The rear OS X should sit at about 0.5VDC while running.

The front one is complex - it is a pulsed signal corresponding the varying oxygen level in the exhaust

Volvo doesn't have a set of specs for that in Alldata at least.

I can probably measure it on the S70 later today

fszczesniak · Post by **fszczesniak** » 19 Mar 2020, 10:40

Precat should be able to jump between 0.1 and 0.9v, but what I mean is, what onboard voltage should precat get from battery/ECU... If it won't have at least 10.5v, it won't operate correctly (source - "Hella" lambda troubleshooting website)

Post by **Clemens** » 19 Mar 2020, 15:06

I habe no clue about the O2 sensor issue, but an old coolant temp sensor can cause abnormally gigh fuel consumption. But then, you seem to have traced it down to the O2 already.

fszczesniak · Post by **fszczesniak** » 19 Mar 2020, 23:12

My sensor is old, but I had visually inspected it not so long ago when I installed a new coolant tank and never had any problems with engine temp readings

fszczesniak · Post by **fszczesniak** » 21 Mar 2020, 12:17

I have noticed lately that my battery is always charging with 13.6V, even after roadtrips (the battery is new) - does it add anything to the problem?

Post by **misha** » 21 Mar 2020, 13:34

Measure directly on alternator with multimeter,BUT after about 30 min of driving and WITHOUT turning the engine off.

Red probe on b+ and black one on alternator housing.

If there is 13.9-14.0v with headlights ON and battery terminals still shows 13.6v,you have a voltage drop.

If you have a voltage drop we will proceed in further investigation.

fszczesniak · Post by **fszczesniak** » 21 Mar 2020, 13:45

Aye, will do and report as soon as possible

Edit: as suspected, the alternator is giving around 13,9-14V, and battery is getting 13,8V (lights ON, car driven for about 30 minutes)

fszczesniak · Post by **fszczesniak** » 04 Apr 2020, 14:11

vida dice data - hot idle
- o2 sensor precat fixed at 0,98v
- o2 sensor postcat fixed at 0,85v

running really rich or what?

Post by **misha** » 04 Apr 2020, 14:54

fszczesniak wrote: ...Edit: as suspected, the alternator is giving around 13,9-14V, and battery is getting 13,8V (lights ON, car driven for about 30 minutes)

You are in accepted limits of voltage drop 0.2v....charging system is healthy.

Post by **misha** » 04 Apr 2020, 14:56

fszczesniak wrote: 04 Apr 2020, 14:11 vida dice data - hot idle
- o2 sensor precat fixed at 0,98v
- o2 sensor postcat fixed at 0,85v

running really rich or what?

Front o2 sensor should go up & down with voltage.
Do you have black smoke from the exhaust at idle?