2004 2.5T inlet air temperature read incorrectly by cheap OBDII?

FrankAZ · Post by **FrankAZ** » 05 Jul 2018, 00:07

Hello -

Over the last 8 months I have been futzing about with my wife's 2004 V70 2.5T FWD. Ever since I began the project I have been puzzled by unexpected inlet air temperature readings provided by my inexpensive OBDII reader. They read much higher than plausible numbers. For example, when outside ambient air was ~80F they would show as ~120F. Even after in the course of other repairs I replaced the Boost Pressure Sensor which I understand to include the temperature sensor used by the ECU and presumably reported to the OBDII tool. Now that temperatures are genuinely in the ~105F range the tool displays inlet temperature as >~130F.

Some thoughts occur....

The reading is correct. Inlet air temperature is really that high. The temperature gain is caused by a combination of warm engine bay air being further heated by the turbo body and gas compression, Gay-Lussac's law. This seems unlikely as the inlet is forward of the engine bay and at idle how hard is the turbo working to compress the air? Also, the odd readings occur immediately after a cold start and way before I would expect engine-derived heat gains to bleed into the system.
The OBDII tool is incorrectly scaling the temperature prior to display on the tool, but the car itself is correctly determining the air temperature and applying the correct segment of the engine map. Everyone's generic tool shows the same wrong values because Volvo or the ECU provider have incorrectly implemented the temperature reporting function.
The ECU believes the incorrect temperature even though actual air temperature is lower so that I am running the car permanently lean. The ST and LT injector adaptations to control stochiometric burn and correct gasses at the O2 sensor converge to ~0.00% so this seems strange.

I've searched this forum and those others which use the same engine. No one has mentioned the same issue in any visible way. Does any one have knowledge to share? I can believe my cheap OBDII tool in all other respects - the only parameter out of whack seems to be the inlet air temperature. The car runs well (now!) but now that I know this issue it lingers in my mind.

Any one else seeing this?

Frank

Post by **RickHaleParker** » 05 Jul 2018, 01:32

#12 ITA (Inlet Air Temperature) sensor. Volvo part number: 9445153.

Post by **abscate** » 05 Jul 2018, 05:03

I’ll bet the OBD tool map is bad. These sensors don’t go bad often, and the tools are notorious for badcodes. I had one that kept telling me my cylinder 8 was misfiring

Post by **jimmy57** » 05 Jul 2018, 06:50

The intercooler is behind a/c condenser so the T from that cooler is not going be ambient very often. The proximity to radiator makes it warmer than ambient even in winter.
Turbo heats air and turbo outlet plumbing to cooler is routed over top of engine. With engine runnning use a water hose on intercooler through grill and watch the temp reading to see that it goes below ambient to prove sensor is responsive.
Read the sensor before engine start and overnight rest and you should see ambient temp if the tool readings are not incorrect.

FrankAZ · Post by **FrankAZ** » 05 Jul 2018, 11:56

Thank you RickHaleParker for the diagram. I had a quick look and verified that my car DOES NOT have item #12 or #4. That section of duct does not have any sensors of any type. It does have a sensor at item #18, though mine is a combined Pressure/Temperature Sensor (Bosch 0261230090), which I have replaced without any change to the IAT reading.

Is there another variant of my 2004 V70 2.5T FWD. My last-9 VIN are 842402310.

Jimmy57: My strange IAT readings occur when the engine is cold and before starting.

Thank you.

Frank

Post by **oragex** » 05 Jul 2018, 13:19

Now that's a strange location on the turbo. Is that the air intake for the turbo itself? On the N/A engines the IAT sensor is located right at the MAF sensor after the air intake filter - www.youtube.com/watch?v=-bejldUOfVs

The IAT in the video was covered with a thick crust when I bought the car, suggest using a small wet ear q-tip

Post by **RickHaleParker** » 05 Jul 2018, 14:51

Frank two questions.
1. Gasoline or Diesel.
2. Is it a 2004 V70R?

It would help if you would get the engine type off the block.

FrankAZ · Post by **FrankAZ** » 05 Jul 2018, 23:46

RickHaleParker wrote: ↑05 Jul 2018, 14:51 Frank two questions.
1. Gasoline or Diesel.
2. Is it a 2004 V70R?

It would help if you would get the engine type off the block.

Sorry for the delay.
1. Gasoline
2. No, a 2004 V70 2.5T A SR (per the Mahoney sticker) V70 2.5T FWD (per common description).
2b. US Spec.

The engine type, according to my interpolation of a grubby partially obliterated label on the timing belt cover, is B5254T2. S/N 3242296, P/N 6900[6?]31.

Thanks for any further info.

Frank.

Post by **RickHaleParker** » 06 Jul 2018, 04:05

I think somebody put the wrong BPS in that car.

In the diagram above the BPS/MAP is #18. If you look at the part list there is a different BPS for the B5254T4.
Volvo part number 31303975 does cross reference to Bosch 0261230090 (B5254T4).
Volvo part number 8677288 cross references to Bosch 31355464 (B5254T2).

However I think I got the answer to the elevated temperatures.

The Bosch 0261230090 is a combination pressure/temperature sensor.
It is used as a (BPS) Boost Pressure sensor & Intake Air Temperature (IAT) Sensor.
It is also used as a (MAP) manifold absolute pressure & Intake Air Temperature (IAT) Sensor.

Used as a BPS it is located between the Turbo and the intake manifold. As the air passes through the Turbo it pick up heat from the exhaust. The intercooler will bring the temperature down but not back to ambient. That is why your seeing temperatures above ambient temperatures.