Volvo V70 o2 sensor problems

[Daniel]

Hi guys, my first post here in the ETCG forum. I love Eric´s videos and can´t wait until he posts another one!

I have run into a problem here in Sweden though, and I thought maybe I could get some info on where to look next to solve this problem.

A friend/customer of mine has a Volvo V70 I Think it´s a -99 or maybe -00 year model.
A while ago the check engine light came on. The code I pulled was P0135. Sensor heater failure. Bank 1, sensor 1.

The sensor has 4 cables. Blue, white, and 2 black ones. I pulled the connector apart and Ohm measured over the 2 black wires. It had infinate resistance. My conclusion was that the heater circuit was indeed bad.

We got a new “universal” sensor. It also has 4 wires of course, 1 black, 1 grey and 2 White ones.
I then Ohm measured over the 2 White wires and got 5,7 Ohm´s of resistance and was happy about fitting the new one that should solve the problem.

I crimped the connectors like this 2 White – 2 black = heater Circuit.

Blue signal (old sensor) – black wire on the new sensor.

White (old sensor) – grey = ground.

Now for the problem, it still sets the exact same code when the check engine light comes back on again.
Did I do something wrong, or is there another problem maybe in the wiring?

Please try to shed some light on this matter fellas!

Thanks

/Daniel

Topic

[Jack Patteeuw]

It is not the sensor. It is the heater circuit. The PCM actuallu does sense current going to the heater. In this case, there is none.

You will need a wiring diagram to find the fuse and or relay that is not working.

[Sam]

interesting, If thats true. If the PCM sense current, then the wrong sensor, or resistance could also give this. Don´t you agree with me?

Daniel, if you unplug the sensor will it sill give the same code?

[Jack Patteeuw]

[quote=”SameSam” post=60833]interesting, If thats true. If the PCM sense current, then the wrong sensor, or resistance could also give this. Don´t you agree with me? [/quote]
Probably not !

O2 Sensors (EGO) are pretty common, even between car companies, with the only difference being the length of the pigtail and possibly the connector.

Some new cars are starting to use “universal” EGO (UEGO) sensors. This sensors do not “switch” at stoichiometry. They give a continuous voltage that varies with with how rich/lean the engine is running.

[Sam]

[quote=”theoldwizard1″ post=60859]Probably not !

O2 Sensors (EGO) are pretty common, even between car companies, with the only difference being the length of the pigtail and possibly the connector.

Some new cars are starting to use “universal” EGO (UEGO) sensors. This sensors do not “switch” at stoichiometry. They give a continuous voltage that varies with with how rich/lean the engine is running.[/quote]

Well now you are talking about Wideband sensors, I’m pretty sure that this 00 Volvo v70 don´t have a wideband sensor ,if its not an aftermarket install. And a 4 wire wideband sensor is pretty rare, 5 is most common.

And I still need to doubt your statement of “It is not the sensor.” Even if this was an Wideband, I would say its even more important that its the original, so its not an narrow-type. But its always good to check power to the heater circuit 🙂

[twiggy]

My Toyota Sienna uses the wideband sensor and it’s 4 wires. There is a decal under the hood with the vacuum routing and it indicates that it uses a “wideband” or “a/f sensor”.

[Jack Patteeuw]

[quote=”twiggy02919″ post=60884]My Toyota Sienna uses the wideband sensor and it’s 4 wires. There is a decal under the hood with the vacuum routing and it indicates that it uses a “wideband” or “a/f sensor”.[/quote]
Whether it is a “wideband”, universal, O2 or egu, UEGO sensor is all semantics.

The bottom line is the heater is not working on the original sensor and on the replacement.

Disconnect the harness (or carefully back probe the connector) and confirm there is V_batt with key on, engine running at the 2 black wires.

[Daniel]

I just had Another go at this thing. When turning on the key, there is a steady supply of 9 Volts going to the heater.
Why 9 Volts?
When viewing “live data” from my scanner, with Engine stopped, the working rear sensor shows a 0.000 Volts signal.
The front sensor Always shows a 0.500 Volt signal. This Reading stays the same when the Engine is running. The rear is switching normally between 0.1 and 0.9.

The cars owner now wants to try a new ECU, but we failed in removing the old one. No matter how much we pried and hammered away at the Purple colored lock tabs it just would not come loose. It´s as if the Connectors are melted or corroded in Place. We gave it a good 2 hours but could not get it loose. I have never seen something like this.

Also the battery is shot, don´t know if this is making matters worse.

What do you guys make of this?

I´m at wit´s end.

[Sam]

Ok, I would still recommend an original O2 sensor before replacing the ECU,. Since I think an ECU would be more expensive to try. But its your choice.

And what do you mean with your battery is shot? Would it effect the voltage readings?

[Daniel]

The battery is old and will not hold a good charge. It will only read 12.1 – 12.2 Volts. And the positive terminal gets hot enough to burn your fingers when the Engine is running.
The alternator´s output voltage is correct though.

Yes, an ECM is expensive, but he was gonna try to get a hold of a used one.

My next step would be to measure the other sensors heater Circuit voltage. Maybe I should have done that already but I missed that.

Come to Think of it, if the connectors are the same, I might try switching them over to see if the problem moves, or remains the same.
If it moves, it should be the wiring/ECM or other, and that would indicate that the new sensor is capable of working.

If it stays the same with the rear sensor wires on the front sensor, I would say it´s the sensor.
Right?

[Daniel]

Hey, just to give you guys an update on the O2 problem with the old Volvo, the guy traded it in for another car at som dealer in another town.

However, I do have a strong feeling now that the fault lied in the wiring, as he had to replace the battery, and after fiddling with the wires (since the car had a battery with the terminals on the wrong sides before) the light Went out for a day or two. Then it came on again and stayed like that for 2 months before he sold it.

So it will be someone elses headache now!

Thanks for the help you provided guys!

/ Daniel

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