code 33
Thread Starter
3rd Gear
Joined: Mar 2009
Posts: 3
Likes: 0
From: Houston Texas
code 33
I am having problems with my ck eng light coming on and when I scan the computer I get a code 33 which is mass air flow meter voltage too high. I have changed my mass air flow meter, the computer and the 2 relays- burnoff and power. After clearing the code, I can drive for 50 to 70 miles and the same code will pop up again. Any ideas on this? NOTE: I have even tried putting the original GM prom back in the computer instead of the Hypertech chip and it stills comes on. HELP
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Clean or replace the air filter....If running an oil charged filter go light on the oil as it can get sucked into the sensor. Make sure that ambiant air is not being sucked into the TB after the sensor. Also inspect or clean the wire contacts for the harness plug that goes to the sensor.
A true code 33 (no problems at all with the entire MAF circuit) is telling you that there is not enough incoming air to cool the platnum filiment within the sensor.....so the sensor sends a high voltage. Descreening a MAF sensor can sometimes have this same effect since the screen acts as a difuser to allow the air to move across the filment more evenly.
A true code 33 (no problems at all with the entire MAF circuit) is telling you that there is not enough incoming air to cool the platnum filiment within the sensor.....so the sensor sends a high voltage. Descreening a MAF sensor can sometimes have this same effect since the screen acts as a difuser to allow the air to move across the filment more evenly.
Thread Starter
3rd Gear
Joined: Mar 2009
Posts: 3
Likes: 0
From: Houston Texas
Clean or replace the air filter....If running an oil charged filter go light on the oil as it can get sucked into the sensor. Make sure that ambiant air is not being sucked into the TB after the sensor. Also inspect or clean the wire contacts for the harness plug that goes to the sensor.
A true code 33 (no problems at all with the entire MAF circuit) is telling you that there is not enough incoming air to cool the platnum filiment within the sensor.....so the sensor sends a high voltage. Descreening a MAF sensor can sometimes have this same effect since the screen acts as a difuser to allow the air to move across the filment more evenly.
A true code 33 (no problems at all with the entire MAF circuit) is telling you that there is not enough incoming air to cool the platnum filiment within the sensor.....so the sensor sends a high voltage. Descreening a MAF sensor can sometimes have this same effect since the screen acts as a difuser to allow the air to move across the filment more evenly.
Team Owner
Joined: Jan 2003
Posts: 20,254
Likes: 220
From: Summerland B.C. Canada
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Code 33 problems
There are a few things that can cause a code 33 which is a high MAF signal. These could include a) an open wire or terminal at or to the MAF; b) faulty relays (or installed backwards and with this I mean there are two different relays used one for power and the other for burn off, and if they are switched I have seen them give code 33, don't know why but I have seen this even though they seem to be the same relay with the exception that one comes with a shock absorbing strap and the other one does not so one thing can be to just swap relays and see if that helps). Relays could be a good possibility and would be worth checking and you also need to try swapping them to make sure they are not the problem.; c) faulty MAF sensor and the last possibility being; d) the ECM.
PROME REVISION - I want to point out that Chevrolet has come out with a revised PROM for the 1986 Corvette due to code 33 problems. Now before you go off and order the revised PROM we need to find out a little bit more of the problem you are having. This is not a hard code to fix but you may have to do a little looking.
WIRING - Wiring is not a common code 33 problem but if you have an intermittent problem that could be a sign of a poor connection of one of the terminals at the MAF sensor. If the light comes on right away that could also be a sign of a broken wire. If one of the MAF sensor wires becomes open it will set a code 33 but, this condition would happen all the time probable shortly after start up. If you have access to a scan tool I would hook it up and read the airflow; when warm it should be around 6.0 grams per second. Then try wiggling the wires and if it shoots up you having a wiring problem. If it's high all the time then you could have an opening in the wiring. I would suspect that seeing how you tried a new sensor that would not be the problem but I would check it anyway to begin with.
ECM Upgrade - I suspect that you have a #1227165 ECM in the car and that could be the problem. This is the original style ECM used in the 86 to 89 Corvettes. Chevrolet has had a real problem with the internal circuit board cracking on these original units and when this happens there can be all kinds of problems including code 33, 36, 34, 15, 51 and a few more. Drop down the ECM and see what the service number of the unit is and if it's a #1227165 replace it, if it's an aftermarket rebuilt painted black one replace it as I do not trust that old style ECM at all and I have found that just about all aftermarket replacement ECM units are of the old style. The GM number you need to go back in the car with is a #16198259 it is the GM replacement for the original #1227165 and is much better.
PROME REVISION - I want to point out that Chevrolet has come out with a revised PROM for the 1986 Corvette due to code 33 problems. Now before you go off and order the revised PROM we need to find out a little bit more of the problem you are having. This is not a hard code to fix but you may have to do a little looking.
WIRING - Wiring is not a common code 33 problem but if you have an intermittent problem that could be a sign of a poor connection of one of the terminals at the MAF sensor. If the light comes on right away that could also be a sign of a broken wire. If one of the MAF sensor wires becomes open it will set a code 33 but, this condition would happen all the time probable shortly after start up. If you have access to a scan tool I would hook it up and read the airflow; when warm it should be around 6.0 grams per second. Then try wiggling the wires and if it shoots up you having a wiring problem. If it's high all the time then you could have an opening in the wiring. I would suspect that seeing how you tried a new sensor that would not be the problem but I would check it anyway to begin with.
ECM Upgrade - I suspect that you have a #1227165 ECM in the car and that could be the problem. This is the original style ECM used in the 86 to 89 Corvettes. Chevrolet has had a real problem with the internal circuit board cracking on these original units and when this happens there can be all kinds of problems including code 33, 36, 34, 15, 51 and a few more. Drop down the ECM and see what the service number of the unit is and if it's a #1227165 replace it, if it's an aftermarket rebuilt painted black one replace it as I do not trust that old style ECM at all and I have found that just about all aftermarket replacement ECM units are of the old style. The GM number you need to go back in the car with is a #16198259 it is the GM replacement for the original #1227165 and is much better.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Thanks, I use a K&N filter and it does not appear to be real dirty. I will still clean it up. I have never cleaned and re oiled it sense I bought it .I will go light on the oil. Have you ever tried a Micro Tech mass air flow meter? It is suppose to produce more air flow, but it would never run good on my vette. Rough cold start. Bosch works much better. I bought it because it had a lifetime warranty.
