Code 23 - Mass Air Temp Sensor (MAT) - VoltageToo High

[jthom263]

Hello everyone!


I performed an engine diagnosis on my '91 VP Commodore today and received error code 23.

I know the easiest way to fix this error is to just replace the MAT sensor but my questions are - Number 1 What exactly does it look like?
Number 2 where exactly is it located on the 3.8L V6 Buick? (Pictures would be good)

Thanks in advance!

Jack

 

[Jxfwsf]

screwed into the plenum on the last runner (#6) on the drivers side of the intake manifold.

 

[Cheap6]

Maybe check that there is actually a consistent fault first? Clear the fault code (remove the ENG COMP fusible link under the bonnet for ~10 seconds or so) and check to make sure that it is cleared. Then drive the car and see if the fault code comes back. If it doesn't, as sometimes happens, it's an intermittent fault. If so, it can probably be ignored if it is not recurring.

If there is a genuine fault, it may not be the sensor (although that is inexpensive to replace). It can be anywhere between the sensor and ECM, including inside the ECM.

 

[jthom263]

Howdy!

Thanks for the speedy replies.

I replaced the MAT Sensor today to no avail, reset the engine computer and that removed the error code but then I started the vehicle ran it for 30 or so seconds at medium-high revs and the engine light re-appeared - after diagnosis found it was again our old friend code 23.

Voltage too High Suggests to me that there could be a component or just a wire failing open on the way to the MAT sensor causing excessive voltage draw. (I'm a Broadcast Electronics Engineer) So the next step I'm going to take is using the schematic diagrams perform a continuity test and a resistance test between the ECU and the MAT sensor. Then that should tell me if there is anything failing open or maybe even short. If I find something I will repair it accordingly. If not I will swap out the engine computer with a spare as the one in the car currently is a non genuine re-manufactured one.

If after all this I still can't find the fault could anyone suggest my next best course of action? What else could be causing this mystical yet disturbing engine light?

Thanks
Jack

 

[Jxfwsf]

Unplug the 2 connectors for the ecu and plug them back in a couple of times to rule out a bad connection there (this'll clean the connections and 85% of the time can fix an issue).

Looking at the schematic the MAP sensor and MAT sensor share the same ground pin to the ecu, Black wire going to pin A11, perhaps unplug the ecu, map and mat sensor, in the engine bay check for continuity between the Black wires on the MAT and MAP plugs.
MAT sensor is signal is wired straight to the ecu to pin C12, you've ruled out the sensor, there's no MAP codes thrown so i'd be checking the gnd.

These old looms do have a tendency to playup in the splice joints, simple copper crimp wrapped with electrical tape, moisture and air have gotten in there by now and possibly tarnished it.

 

[pete30nz]

Hi people,
Tonight I went to get dinner, my car seemed to be driving normally.
Hopped back in car, when I started it, it stalled.
Tried starting it and turned over, but didn't fire.
Waited and it started again, went to reverse and it stalled again.

I have code 23 - iat high voltage

Pulled the plug off the iat sensor, pulled the ecu fuse to clear codes, started car, it ran for a good 5 seconds then stalled...

Any ideas please, thanks in advance

Pete

 

[91SS]

If you try another ECU get an exchange reco one for around $180.
Edu issues cause lots of problems on these cars.
Good luck.