trouble code 34 check a failure?
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 18
Likes: 0
From: Tallahassee Fl
trouble code 34 check a failure?
http://www.chevythunder.com/maf_code_34.htm
Car wont stay running and I got a trouble code 34, well when I did this check I kept getting only a code 34 all the way through until the end even though that isn't an option on the list. anyone know if this is a good test or if there could be another problem? also, my car wont run more than 5 seconds with the MAF sensor unplugged.
Car wont stay running and I got a trouble code 34, well when I did this check I kept getting only a code 34 all the way through until the end even though that isn't an option on the list. anyone know if this is a good test or if there could be another problem? also, my car wont run more than 5 seconds with the MAF sensor unplugged.
Melting Slicks
Joined: Aug 2003
Posts: 3,399
Likes: 395
From: Lakeville MI
After the first test results in setting a Code 34, clear the codes first and verify with Code 12 before running the second test.
With no stored codes and the MAF disconnected (open circuit) you should get a Code 33 if ecm 5 volt pull-up is working and there is no short to ground.
A code 34 under these conditions would indicate a short to ground on the MAF signal wire.
With no stored codes and the MAF disconnected (open circuit) you should get a Code 33 if ecm 5 volt pull-up is working and there is no short to ground.
A code 34 under these conditions would indicate a short to ground on the MAF signal wire.
Melting Slicks
Joined: Aug 2003
Posts: 3,399
Likes: 395
From: Lakeville MI
The procedure as shown in the link is flawed. It skips the step where you are supposed to clear codes between tests.
Try this instead (with thanks to Agent86):
http://members.shaw.ca/corvette86/Code%2034.pdf
Try this instead (with thanks to Agent86):
http://members.shaw.ca/corvette86/Code%2034.pdf
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 18
Likes: 0
From: Tallahassee Fl
still showing a 34 and definitely have a short in the ground. how exactly should I reground the MAF sensor? do I just splice into the ground wire, and if so where do I run the new wire too?
Thanks for your help
Thanks for your help
Melting Slicks
Joined: Aug 2003
Posts: 3,399
Likes: 395
From: Lakeville MI
Based on the info provided, you have a short to ground on the MAF signal wire (green wire), Not a short in the ground. No need to reground, unless ground is open or somehow shorted to Vbatt.
Here's another test:
With the MAF disconnected and IGN On (engine not running), you should have 5 volts on the green wire which is provided by the ECM's pull-up resistor on this circuit.
Check voltage on MAF signal wire in the state described (MAF disconnected,
IGN On, engine off). If you have 5 volts, then signal wire is not shorted and ECM pullup is operational.
If this wire is shorted to ground as suspected by preceding tests, you should see 0 volts on the green wire and also have continuity to ground. Check the voltage first. If zero, check for continuity (low resistance) to confirm short.
If zero volts, and no continuity to ground then there is an issue with the ECM's 5 volt pullup.
Here's another test:
With the MAF disconnected and IGN On (engine not running), you should have 5 volts on the green wire which is provided by the ECM's pull-up resistor on this circuit.
Check voltage on MAF signal wire in the state described (MAF disconnected,
IGN On, engine off). If you have 5 volts, then signal wire is not shorted and ECM pullup is operational.
If this wire is shorted to ground as suspected by preceding tests, you should see 0 volts on the green wire and also have continuity to ground. Check the voltage first. If zero, check for continuity (low resistance) to confirm short.
If zero volts, and no continuity to ground then there is an issue with the ECM's 5 volt pullup.
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 18
Likes: 0
From: Tallahassee Fl
as you can already tell, I am not much with electrical stuff so I need verification that I did the above procedures correct. I unplugged the MAF, set my multimeter to the ~v 20 setting in the DC mode, turned my IGN on, then placed the red needle to the green wire and the black one to the battery ground and the multimeter only read .135 v. did I do this correct? if so, does this mean that I have a short to the ground?
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Safety Car
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2 things.....
did you go thru the MAF relays? power relay? not sure if 89 had a burn-off or not.
next, you have to force the engine to run about 8-10 seconds with the MAF unplugged so it can set itself to LHM and run on the cal-pak thats in the ECM.
IF your flash codes show a good ECM...code 12 up front and at the end, and the ECM will NOT shift to limp home mode, then you need to look at the harness power source connections and then the grounds. Power is supplied to the engine controls from separate wires behind the battery with fusable links under the battery. Find the wire for the ECM power.
Next, do you see the various grounds in the FSM drawings? Those are too detailed to miss anything. Use those drawings to trace the power and grounds to/from the ECM and the MAF.
I suspect this is a harness issue...broken wire, damaged. Assuming that all fuses and links have been looked at, if the ECM will not shift modes then I question if its even in the loop at the run position.
did you go thru the MAF relays? power relay? not sure if 89 had a burn-off or not.
next, you have to force the engine to run about 8-10 seconds with the MAF unplugged so it can set itself to LHM and run on the cal-pak thats in the ECM.
IF your flash codes show a good ECM...code 12 up front and at the end, and the ECM will NOT shift to limp home mode, then you need to look at the harness power source connections and then the grounds. Power is supplied to the engine controls from separate wires behind the battery with fusable links under the battery. Find the wire for the ECM power.
Next, do you see the various grounds in the FSM drawings? Those are too detailed to miss anything. Use those drawings to trace the power and grounds to/from the ECM and the MAF.
I suspect this is a harness issue...broken wire, damaged. Assuming that all fuses and links have been looked at, if the ECM will not shift modes then I question if its even in the loop at the run position.
Thread Starter
Heel & Toe
Joined: Feb 2013
Posts: 18
Likes: 0
From: Tallahassee Fl
well it has taken me a while to get to this, but I just went out in the 30 degree florida weather (doesn't sound right) and finally got a code 33. I have been getting a code 34 regardless of what I do lately, but I cleared the codes, unplugged the MAF and got the car to run for several minutes in order to get something other than a 34. would a code 33 absolutely mean a faulty MAF sensor at this point? just changed that thing 4 years ago 