I know this is a Corvette Forum but I need some help with a Code 34. I have an 86 Camaro Iroc with a 5.0 TPI. Have an issue where the car will want to stall when warm and I have a code 34. Car has 66,000 miles and I discovered the code 34 when I was working on the dash. I found the bulb out for the Service Engine Light. I just purchased the car in October. The car has only been driven about 1,000 miles since 2001. Since I discovered the Code 34 I have done the following.
Replaced MAF with a reman Bosh Unit. No change
Replaced the Injectors, Fuel Filter, Fuel Pressure Reg. and all O rings in the fuel rail. No change
Cleaned IAC and set TPS. No Change
Deleted the Cold Start Injector. No Change
New chip and tune from Tuned Performance, No Change
Swapped out the ECM, No Change
Sent logs to Brian from Tuned Performance from Tuner Pro RT
Logs show that the GPS are off from the MAF.
I connected my Vacuum gauge and it showed that Vacuum is low so I figured a Vacuum leak.
Smoke tested the intake and it showed that the Intake had a leak.
I sprayed Brake Cleaner where the smoke was coming from and the idle smoothed and the GPS went normal.
Pulled intake, Runners, Plenum etc....
Replaced all gaskets.
I haven't got a chance to drive it yet after the intake gasket was replaced bc I have a valve cover leaking.
On start up I still have a code 34.
Brian from Tuned Performance and I are stumped.
Anyone have any suggestions on what it could be.
Also, I ohm tested the wire from the Mass Air Flow Sensor to the ECM and it is good.
Any help would be awesome

Thanks

Pete

 

@tequilaboy do you happen to know the threashold for code 34. His idle shows 3.5 gps with a few different mafs. He had sprayed carb choke cleaner it seemed to go to 6 gps for seconds then drop down.

 

Code 34 compares the MAF A/D counts * 7 to a threshold of 49. So if the raw A/D count is < 7 it will fail. 1 A/D count is about 20 mv, so MAF voltage < 140 mv will set the dtc.

At 3.5 gm/s you're down in the mud between 0 and 180 mv (in MAF table 1). Compare the unlimited airflow signal against the normal MAF signal. If the unlimited airflow signal is fixed (presumably at a low value), that is a good indication that the MAF signal is reporting the default airflow calculated value instead.

Note: there is also a min MAF parameter set to 3 gm/sec.

Edit: 5.0 f-body tuning may be slightly different than the C4 values shown above. Sorry, I didn't think to check a 5.0 bin.

 

@tequilaboy Any idea how to fix what what it is doing ? I’m lost with all that I have done already. I can’t seem to find the cause. I thought the vacuum leak on the intake manifold would have cured it.

Thanks

 

I suspect that you're dealing with an un-powered MAF. Check the MAF power relay.

 

Btw to note the bin is now updated to $6e apym

 

@tequilaboy I’m pretty sure I checked that I was getting 12 volts to the MAF
Any help with how to check for the proper power to MAF ?

 

Check both of the grounds at the MAF connector.

You could try unplugging the MAF and starting the car to verify that it will set a Code 33 in order to test the integrity of the ecm input circuitry, pull-up resistor and A/D converter. If you log data while doing this you should see the unlimited airflow signal go sky high (254 and stay there) while the MAF airflow signal will be limited initially by the max maf vs rpm table (15-28 gm/sec tuning/rpm dependent) and then be replaced by the default airflow calculation that should allow the car to run.

 

@tequilaboy What do you mean by A/D ?
Also I ran the car with the Mass Air Flow sensor unplugged and got code 33. I haven’t ran it unplugged since I fixed the vacuum leak. I can give that a try. I’ve been data logging with Tuner Pro RT.
what should my readings be with the engine running at the mass air flow sensor plug ?

 

Use a volt meter between purple wire pin E of the maf to pin A then to pin B of the maf to check the maf power and grounds.

 

Noteworthy: 3.5 gm/sec happens to be the default airflow offset value in APYM, so this is likely the value that has been observed and described above.

3.5 gm/sec would be within the valid voltage range if this was from the actual sensor signal.

Rough interpolation of APYM MAF table #1 (partial table shown):

A/D Volts MAF Table1 Row #
0 0 6.02 0
1 0.02 5.72
2 0.04 5.42
3 0.06 5.13
4 0.08 4.83
5 0.1 4.54
6 0.12 4.24
7 0.14 3.94
8 0.16 3.64
9 0.18 3.35 1
10 0.2 3.46
11 0.22 3.57
12 0.24 3.68

You could try reducing both of the Code 34 error thresholds to something like 21, 28, 35 or 42 (multiples of 7) if you think you have a functioning MAF with borderline output or very low actual airflow through the sensor (or larger housing diameter).

Also wouldn't hurt to add the MAF A/D counts (L00F3) or MAF A/D counts * 7 (L00F5) to the datastream to better see what is going on.

;--------------------------------------------------------
; ERR # 34 Params
; >> MAF Sensor Lo <<
;--------------------------------------------------------
LC215 FDB 0049 ; 0049 COUNTS, IF ANALOG CNTS x 7 or
; PP2 DLT LT 0 SET ERR 34B
;
LC217 FCB 10 ; ERR #43, 1 Sec Min time req.
; cal + Arg * 10
;
LC218 FCB 24 ; If RPM > 600, Ck ERR #34B
;
LC219 FCB 16 ; If TPS > 6.25%, Ck ERR #34B
; cal = Arg * 2.56,
;
LC21A FCB 0 ; If LV8 >= 0, Ck ERR #34
LC21B FCB 130 ; If LV8 <= 130, Ck ERR #34B
;
LC21C FDB 0049 ; 0049 COUNTS, IF ANALOG CNTS x 7 or
; PP2 DLT LT 0 SET ERR 34A

 

@tequilaboy I will see if @Tunedperformancedotorg to make those changes. I’m not sure what you mean by
“Also wouldn't hurt to add the MAF A/D counts (L00F3) or MAF A/D counts * 7 (L00F5) to the datastream to better see what is going on.”

I think Tuned Performance said he could turn off code 34. Just need it to not want to stall.