Hello everyone. I've got a 93' 940 turbo wagon. I have heard about bad airbox thermostats causing the flapper valve to get stuck and frying the MAF.

When I pull codes, I get one for 'air temp sensor signal faulty or absent'. Is this 'air temp sensor' in any way related to the MAF (is it integral to the maf) or is there another one somewhere else?

If my airbox has a thermostat, in which case it would also have a flapper valve, do I have to take the whole box out to access it?

Any help is always appreciated.

On a side note. I recently had my car in for some work and asked the guys to pull the codes. They came back to me and said that there were no codes present. Apparently they scanned my ECU with whatever they have. Can you do that? And why would there be no codes when they scanned it but there still be codes if I pull them from the OBD thing near my ABS?

 

Dear deewolfz:



My experiences with the Air Box Thermostats I needed to get an Air Box valve system as mine was missing. I went to the various wreckers and things I found all the thermostats were frozen and most of the valves were damaged some boxes were damaged but I fund a unit that was intact and pulled it out. These Thermostats have a short life as to putting in the thermostat with out removal I found the removal of the box to be not a problem on a 1992 240 GL with the BF230 engine Your turbo most likely will be different so the issue of taking out the box is not with in my expertise. I would expect that an overheated air flow into the MAF to damage it.

 

the turbos shouldn't have that air flap thing at all, at least my 92 745T and my son's 91 940SE (965T) don't.

theres no 'dryer duct' tubing going from the exhaust manifold to the airbox

your air temp sensor is on the head under the intake manifold, probably under the cylinder 3 intake tube, but on different models it moves around (there's also the knock sensor, and sometimes another sensor in the 3-4 possible places for such to be mounted). According to my 1992 740/940 schematic, the B230FT EFI Temp Sensor has a red-black wire that goes to the ignition control unit's pin 2, and a green-white wire that goes the LH-Jetronic 2.4 ECU's pin 13

With this sensor malfunctioning, you likely would have lousy running when the engine is cold.

 

Thanks Keith and Pierce. I never noticed any piping running from the exhaust to my airbox but just wanted to be sure there wasn't a different setup on the turbo engines.

I think you're right about the air sensor being under number 3. I know the coolant sensor for the dash is under number 2 on the block and I know where my knock and oil pressure sensors are. I will look for that red-black wire and see what I can find.

thanks again!

 

oh geez, wait. AIR temp sensor. belay what I said about the block, thats not air temp. in fact, I don't believe these cars even HAVE an air temperature sensor. they have an air mass meter instead.

what OBD code did you get?

 

I don't remember the sequence off hand. Yes I have the Bosch MAF with 6-pin connector. I was wondering if there is an air temperature sensor internal to that, that may have gone bad and is sending an infinite or incorrect temp to the ECU.

Here is the code I get

1-2-2
According to a post in volvoforums.org.uk it's: Air temperature sensor signal faulty or missing

 

was that a pin 2 (EFI) or pin 6 (ignition) code? oddly, its not even on the table I use, Engine and OBD Diagnostic Codes

ah, this, Engine and OBD Diagnostic Codes says its a Regina-only code, but I thought you had a 940 turbo, that can't be Regina... are you sure you read that right?

 

I cannot remember which pin it was, but I remember that was the code I got. I know, I have the LH2.4. I will check it again tomorrow and right it down. I have two OBD modules, one is labeled A and the other B, they both have the same amount of ports but only 2 of the ports actually give back a code on the B module. Is this normal?

 

yeah, the other one is ABS or climate control or something. if you shine a bright small flashlight in the holes, you'll see most of them aren't even wired up.

ahhh, found this table saying which module is what. of course, it doesn't give the socket numbers...

Data link connector (DLC)

DEFAULT-ENTITYSystem&/emph;DEFAULT-ENTITYData link connector (DLC)&/emph;
ABS - A
LH2.4/EZ116K - A
Rex/Regina - A
Motronic 1.8 - A
AW 30-40, AW 30-43 - A

SRS - B
Cruise control - B
Parking heater 091-B/D - B
Power seat - B

and naturally, most cars don't have half this stuff. AW30-40 is the electronically controlled automatic used in 960s. Both LH2.4 EFI and EZ116K Ignition codes _should_ be on DLC A not B. I've never seen a 'parking heater' on a US car, this is a separate gasoline powered heater that heats and pumps coolant through the engine and the interior heater so as to preheat your car on a timer on a cold morning in the frigid nordlunds.

hmmm. if you have cruise control, diagnostic code 1-2-2 is "Vehicle speed has not exceeded 35 km/h or vehicle speed signal missing.". I don't see a 1-2-2 listed for ABS or for Cruise Control or for SRS (Airbags)

ah, memory power seats, 1-2-2 means "Position Sensor Motor 3 signal absent or faulty" (motor 3 is the up/down on the back edge of the seat)

you should be getting a 1-1-1 (or fault codes) at from DTC A position 2 and 6. key off, insert the probe, key to position II without starting the car, and press the button for more than 1 but less than 3 seconds (thousand 1 thousand 2 works for me), then wait (patiently) for the blinks.

 

Ok so I just checked the codes for all the pins just to be safe.

Module/DLC A
Pin2: 1-1-1
Pin3: 1-2-5
Pin6: 2-1-4

Module/DLC B
Pin2: 1-2-2
Pin5: 1-1-1
Pin6: even though it is wired up, there is absolutely no response from it... no light unless I hold down the button.

thanks for sticking with this

 

All I recognize is an erratic crank sensor code which may mean something or not. I'd clear all the codes...as there is no way of knowing how old they are...and see what comes back.
Interesting on the hot air ducting...my 91 740T had it and all older cars had it. I wonder if this is the time when Volvo embraced the egr? I run a turbo air box on my V8...I simply drilled a hole through the flapper and the tube it rests against when closed. Took a BLACK wire tie and zipped it closed. The hot air hose is non existent of course and I plugged the air box hole.

 

i haven't found anything saying what the pin numbers on DLC B are, the docs I was reading just said to plug the Volvo scantool in :-/

DLC A pin 2 is EFI, no code, good.

DLC A pin 3 is ABS, code 1-2-5 means "Faulty signal from at least one wheel sensor", I'd clear it and see if it comes back.

DLC A pin 6 is Ignition, 2-1-4 means engine RPM sensor, which is behind the engine block, reading off the top of the flywheel.

Volvo gives the possible reasons for code 2-1-4 as: damaged or scored flywheel, loose connections or bad wiring, rpm sensor incorrectly installed with too much clearance. Symptoms are: difficult or no start especially when warm, engine running jerkily.

the TYPICAL reason from what I've gathered is, the sensor or the wiring is cooked by heat. You might just clear this code and see if it comes back (hold the button down 5+ seconds, then key off, key back to II and press it ~2 seconds and verify you get 1-1-1), drive for a few days and see if this code 2-1-4 comes back.

 

I cleared the codes and they still came back.

I plugged the cable into the corresponding port and held the button for about 6 seconds then released it. Then the light became solid. I turned the key to off then turned to on and checked the codes again. Is that the correct procedure or am I supposed to press the button on the module again while the light is solid?

I just replaced the crank speed sensor about 3,500 miles ago so that's probably why it's throwing that code. I also changed my front rotors recently and noticed that the hub was in pretty bad shape so maybe that's throwing the ABS code.

I had my mechanic (who is part of a volvo specialist shop) watched me pull the codes and then he pulled it into the bay and used his scanning tool and said that there were no codes at all.

How can that be? showing codes on the OBD in the engine bay but showing nothing with the scan tool? Does the scan tool scan something else?

Also, one of my main questions was: Is there an air temperature sensor that is part of the Mass Airflow Meter or is there one that is separate from the whole intake system?

Thanks again guys...

 

none of those codes have anything to do with air temp. the 1-2-2 code is on a different subsystem entirely.

1-2-2 on a DTC B pin *might* be power seats (again, I can't find a reference as to what pin on the DTC B box is which subsystem), 1-2-2 power seats means "Position sensor, motor 3, signal absent or faulty." ... To clear a code on the power seat, ignition off at least 5 seconds; press and hold any seat button, and turn the ignition on, hold the seat button at least another full second, then read the codes again within 60 seconds. phew. you might have to do this for both seats (if you have dual power seats) as the code doesn't say which one is throwing the fault.

1-2-2 also could be cruise control, "Vehicle speed has not exceeded 35 km/h or vehicle speed signal missing"

 

Well, you started out right. After the light stays on solid, hold the button down again for the same length of time. After releasing, it will turn off. Then, to make certain the codes are gone, go through the sequence of checking codes again. You should get 1-1-1 if all codes are gone. When you're finished then turn the key off. As for codes...it is quite possible your mechanic does not have the appropriate scanner. The last, excellent scanner for Bosh FI was the Master Tech. Very few shops still have one; not only are they for obsolete technology, they are getting old and there is no tech support for 'em. His scanner may just not be able to communicate.