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[Migalot]

Some months ago, I had issues with a warning light telling me that there was a fault in the O2 sensor circuit (Bank 2,Sensor1). I had a new Bosch sensor fitted and all seemed well – until last night when the light came on again. I completed my long journey to Oxford and back and the car ran perfectly, despite the light.
This morning, I ran the OBD reader again: 

P0150-08 - O2 sensor circuit malfunction (Bank 2 Sensor 1). Status:Present
P0173-03 - Unknown Error. Status:NotDetected
P0150-07 - O2 Sensor Circuit Slow Response (Bank 2 Sensor 1). Status:NotDetected
P0173-09 - Fuel trim malfunction (Bank 2). Status:Present

I cleared the codes and restarted the car and the light is currently out.

Any thoughts?

[Doctor Gollum]

Any other running issues?

What fuel are you currently using?

Last plug and air filter change?

[Migalot]

Any other running issues?

What fuel are you currently using?

Last plug and air filter change?

No other issues.
97 Premium
June 22 (by James V6 CDX). Included new fuel filter.

 

[JamesV6CDX]

Any other running issues?

What fuel are you currently using?

Last plug and air filter change?

No other issues.
97 Premium
June 22 (by James V6 CDX). Included new fuel filter.

 

Can your Bluetooth scanny jobbie look at live data? If so can you post all the fuel trim values - especially long term fuel trim (LTFT)

[Migalot]

Looks like 2%, James.

[Migalot]

Been out for a couple of trips and no sign of the warning light again.
Definitely gremlins at work!

[JamesV6CDX]

I can’t read those screenshots - can you WhatsApp them please

[LC0112G]

Intake air temperature looks a bit warm/wrong - 30DegC at the moment?

[Doctor Gollum]

I can’t read those screenshots - can you WhatsApp them please

Just click on them

Intake air temperature looks a bit warm/wrong - 30DegC at the moment?

Nah, engine is almost upto temp 82°C and the throttle body has coolant running through it.

[LC0112G]

Intake air temperature looks a bit warm/wrong - 30DegC at the moment?

Nah, engine is almost upto temp 82°C and the throttle body has coolant running through it.

Perhaps - I'm not familiar with that engine. Sanity check is to check the IAT is similar to CTS before starting the car after it's been left overnight. But AIUI the coolant in the throttle body is to stop it icing up in cold weather. With 2.6L of air passing through the throttle body 5 times a second (ish) unlikely the air is really being heated by 20 DegC. Always assuming this is being done outdoors in a well ventillated area.

The LC typically only shows 30 degC IAT whilst it's being ragged during a summers track day. If the IAT sensor reads warm, the ECU leans off the mixture (because warm air is less dense so contains less oxygen per litre). The Lambda sensors then notice the lean mixture and the ECU increases the fuel trims to restore stoic. So a duff IAT sensor can lead to apparent lambda sensor issues.

[Migalot]

Intake air temperature looks a bit warm/wrong - 30DegC at the moment?

Nah, engine is almost upto temp 82°C and the throttle body has coolant running through it.

Perhaps - I'm not familiar with that engine. Sanity check is to check the IAT is similar to CTS before starting the car after it's been left overnight. But AIUI the coolant in the throttle body is to stop it icing up in cold weather. With 2.6L of air passing through the throttle body 5 times a second (ish) unlikely the air is really being heated by 20 DegC. Always assuming this is being done outdoors in a well ventillated area.

The LC typically only shows 30 degC IAT whilst it's being ragged during a summers track day. If the IAT sensor reads warm, the ECU leans off the mixture (because warm air is less dense so contains less oxygen per litre). The Lambda sensors then notice the lean mixture and the ECU increases the fuel trims to restore stoic. So a duff IAT sensor can lead to apparent lambda sensor issues.

You guys know far more than me! 

However, it seems IAT sensors are not that expensive so may be worth getting it changed. Where is it located on the 2.6 and anyone have a part number?

TIA. 

[JamesV6CDX]

I'm having a total mental block (I'm really hungover today), but isn't the air intake temp sensor integrated with the MAF on later models?

[Doctor Gollum]

Intake air temperature looks a bit warm/wrong - 30DegC at the moment?

Nah, engine is almost upto temp 82°C and the throttle body has coolant running through it.

Perhaps - I'm not familiar with that engine. Sanity check is to check the IAT is similar to CTS before starting the car after it's been left overnight. But AIUI the coolant in the throttle body is to stop it icing up in cold weather. With 2.6L of air passing through the throttle body 5 times a second (ish) unlikely the air is really being heated by 20 DegC. Always assuming this is being done outdoors in a well ventillated area.

The LC typically only shows 30 degC IAT whilst it's being ragged during a summers track day. If the IAT sensor reads warm, the ECU leans off the mixture (because warm air is less dense so contains less oxygen per litre). The Lambda sensors then notice the lean mixture and the ECU increases the fuel trims to restore stoic. So a duff IAT sensor can lead to apparent lambda sensor issues.

That's a fair observation, but if it has been sat idling with the bonnet closed for a period of time then it will certainly be warmer than ambient.

Whether 30°C is high or not is a moot point given the snapshot because as you suggest the ideal is to start from cold and watch it warm up.

[Doctor Gollum]

I'm having a total mental block (I'm really hungover today), but isn't the air intake temp sensor integrated with the MAF on later models?

That thought also crossed my mind, and I wonder if unplugging it would serve any useful purpose...🤔

[LC0112G]

I would just do the sanity check first before replacing anything. 30 seems hot to me, but I don't know that engine type.

Leave the car overnight. Next morning plug in your scan tool, and BEFORE YOU START THE ENGINE watch the Coolant and IAT temperatures. If both are giving similar and sensible readings (I would guess circa 10 degC outside at the moment), start the car. Continue watching both. Coolant should rise to 80-90, and IAT may rise a little - depends how much effect the throttle body heating has. If the IAT stays at 30 all the time, then it's probably goosed.

I would not just go around replacing things willy-nilly, if for no other reason that 20 year old plastic connectors that have never previously been disturbed can and will break as you wrestle to get the wretched things apart. And then you will have to replace something, even if it wasn't broken in the first place.