Intake air temp sensor, Second location ?

Nick118

New member
Hey guys,

First post! Just picked up a 2004 2500 226k

Been doing a lot of reading on the intake air temperature sensor, I'm getting code p0097.

The full readout is "intake air temperature sensor 2" I replaced the sensor right by the driver side headlight. My scan gauge is showing at 299° on intake air temperature. If I clear the code it will run fine for a bit or it'll just keep faulting.

Is there more than one sensor is the question? Does the mass airflow also read temperature or is there a sensor before the intercooler?

Thanks guys!
 

Arnie_Oli

Member
I presume this is the one you've already swapped out?

https://sprinter-camper.com/replacing-intake-air-temperature-sensor/

I am no expert on things but my understanding is that MAF sensors read air density coming in to the engine and return a voltage back to the ECU which can be read on a diagnostic unit.

I don't know of another air temp sensor other than the ambient on attached to the bumper. May be worth disconnecting that and seeing what happens to your reading. I had a look through spare parts at the usual shops and can't see another air temp sensor for sale.


Sent from my iPhone using Tapatalk Pro which means I am probably lying under the van wishing I had a crawler and a large warm workshop I could park in.
 
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Aqua Puttana

Poly - Thread Finder

Arnie_Oli

Member

autostaretx

Erratic Member
In Sprinter-speak (i.e. what you find in this service manual: http://diysprinter.co.uk/reference/2006-VA-SM.pdf ):

The sensor behind the license plate is the Ambient Air Temperature Sensor

The sensor on the battery side of the radiator/intercooler is the Intake Air Temperature Sensor (IAT on a scangauge)
((and its usual reading is up to twice (in F) the ambient temp))
(the service manual also refers to that as the Charge Air Temperature sensor)

The pressure sensor next to the IAT is the Manifold Absolute Pressure (MAP) sensor
(the service manual also refers to that as the Charge Air Pressure sensor)
... you can calculate "boost" by subtracting the ambient pressure, but the engine only cares about MAP.
The ambient pressure is measured by both the Barometric pressure sensor that's inside the ECM itself, and the Air Intake Pressure Sensor mounted on the air cleaner box (near the Mass Air Flow (MAF) sensor).

--dick
 
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Nick118

New member
I presume this is the one you've already swapped out?

https://sprinter-camper.com/replacing-intake-air-temperature-sensor/

I am no expert on things but my understanding is that MAF sensors read air density coming in to the engine and return a voltage back to the ECU which can be read on a diagnostic unit.

I don't know of another air temp sensor other than the ambient on attached to the bumper. May be worth disconnecting that and seeing what happens to your reading. I had a look through spare parts at the usual shops and can't see another air temp sensor for sale.


Sent from my iPhone using Tapatalk Pro which means I am probably lying under the van wishing I had a crawler and a large warm workshop I could park in.
That's the one I replaced!! 👍
 

Nick118

New member
Thanks for the replays!
It's definitely an intermittent problem, cleared the code this morning came right back within two minutes.

IAT reading 299f then would go back to pretty close to the ambient air temperature within 5°. Then it would just go right back to 299f. parked the van all day IAT was spot on and working great for about 10 miles then back to 299f.

When the sensor was reading correctly, I unplugged the sensor the default when not plugged in is 299.
It's a brand-new OEM sensor, I checked the wiring from what I can see before it goes into the main wiring loom all looks OK.

Going to check continuity off the ecu tomorrow. 8w-30 is the page in the manual with the diagram.
 

Nick118

New member
In Sprinter-speak (i.e. what you find in this service manual: http://diysprinter.co.uk/reference/2006-VA-SM.pdf ):

The sensor behind the license plate is the Ambient Air Temperature Sensor

The sensor on the battery side of the radiator/intercooler is the Intake Air Temperature Sensor (IAT on a scangauge)
((and its usual reading is up to twice (in F) the ambient temp))
(the service manual also refers to that as the Charge Air Temperature sensor)

The pressure sensor next to the IAT is the Manifold Absolute Pressure (MAP) sensor
(the service manual also refers to that as the Charge Air Pressure sensor)
... you can calculate "boost" by subtracting the ambient pressure, but the engine only cares about MAP.
The ambient pressure is measured by both the Barometric pressure sensor that's inside the ECM itself, and the Air Intake Pressure Sensor mounted on the air cleaner box (near the Mass Air Flow (MAF) sensor).

--dick
The link for the manual is a huge help! Going to check the ecu wiring tomorrow!
 

autostaretx

Erratic Member
IAT reading 299f then would go back to pretty close to the ambient air temperature within 5°. Then it would just go right back to 299f. parked the van all day IAT was spot on and working great for about 10 miles then back to 299f.
That sounds like either a wire is shorting out (the sensor resistance goes lower at higher temperatures, so "zero ohms" would be pretty toasty) or it's shorting to ground (at which point the value 302 F (150C) is substituted.... which your 299 sounds like... (switch your gauge to C))

Here's the book on the IAT sensor:

IntakeAirTemp.jpg

--dick
p.s. the MAF sensor does not provide a "voltage" as its signal... it's a pulse train that varies in frequency and duty cycle (on/off ratio)... the voltage is constant.

MAFsensorTop.jpg

MAFsensorBot.jpg

(above "book" images extracted from http://www.diysprinter.co.uk/reference/T1N_service_scans/ )
 

Nick118

New member
That sounds like either a wire is shorting out (the sensor resistance goes lower at higher temperatures, so "zero ohms" would be pretty toasty) or it's shorting to ground (at which point the value 302 F (150C) is substituted.... which your 299 sounds like... (switch your gauge to C))

Here's the book on the IAT sensor:

View attachment 87586

--dick
p.s. the MAF sensor does not provide a "voltage" as its signal... it's a pulse train that varies in frequency and duty cycle (on/off ratio)... the voltage is constant.

View attachment 87587

View attachment 87588

(above "book" images extracted from http://www.diysprinter.co.uk/reference/T1N_service_scans/ )

Thanks for all the replays guys! The link to the manuals are a big help!

I found what looks like a shot in the wire, when the wires come out of the ECU and make a bend they touch on the bracket where the clutch pedal would go in a five speed. It had the tiniest little hole in Jacket of the wire, I fixed two wires.
I cut out the bad spot just to make sure the wire was not oxidized. So far so good over the last 50 miles!

I checked continuity on both signal and ground wires all good!

You guys might want to look under the dash and check to make sure you don't have any wires rubbing that bracket!

Thanks for the help!!
 

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