Still having MAF sensor burn off problems...
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Still having MAF sensor burn off problems...
Hey guys, I have a 1985 Corvette and I'm having problems with the MAF sensor burn off function.
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Hey guys, I have a 1985 Corvette and I'm having problems with the MAF sensor burn off function.
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
When I cycle the ignition from on to off with the engine off, I get about 5 volts on that wire for 5 seconds. When I let the car get into closed loop, I tested the wire as I shut it off and it goes to about 2.5 volts for only 2 seconds and then back to about 5 volts for the other 3 seconds.
Any ideas?
Thanks.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
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Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Everyone online is saying that it doesn't set a code for the burn off module. Only a code if the wire inside gets damaged which is the same wire that gets burned off. But nothing for the module itself failing or any power/ground/signals going to the module. I'd like to get this figured out as I believe it may help improve my driveability of the car.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
It does not glow after I have someone shut it off in closed loop.
All Data says it is supposed to glow.
I put the sensor on the bench and powered up terminals E and D, and put ground to terminal A and the sensor glowed a very bright orange.
All Data says it is supposed to glow.
I put the sensor on the bench and powered up terminals E and D, and put ground to terminal A and the sensor glowed a very bright orange.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
I dont know what to tell you I do know if it were my car and no light on and the car was running fine I would not worry about it but it is your car do as you please. You might try putting a dab of grease on it drive it like normal for a few days then check it see if it has burnted off
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Maybe it's different for '85, but in my car the ECM measures the output voltage from the MAF while it's doing the burnoff. If that voltage is not correct then it sets error code 36.
I looked at the error code reference chart for '85s and it shows error code 36 as MAF burnoff fault, so it appears your car does the same test.
I looked at the error code reference chart for '85s and it shows error code 36 as MAF burnoff fault, so it appears your car does the same test.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Maybe it's different for '85, but in my car the ECM measures the output voltage from the MAF while it's doing the burnoff. If that voltage is not correct then it sets error code 36.
I looked at the error code reference chart for '85s and it shows error code 36 as MAF burnoff fault, so it appears your car does the same test.
I looked at the error code reference chart for '85s and it shows error code 36 as MAF burnoff fault, so it appears your car does the same test.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
If I am getting 7 volts when it's not plugged in, and 0.8 volts when it is plugged in then there is resistance somewhere. I did the calculations and it goes like this:
7 volts source voltage
1990 ohms on burn off wire in sensor from terminal D to terminal A.
.8 volts / 1990 ohms = 0.0004 total amperage
7 volts / 0.0004 amps = 17500 total resistance
17500 total resistance - 1990 MAF sensor resistance = 15510 resistance left in the circuit
0.004 total amperage x 15510 unknown resistance = 6.204 voltage drop
7 volts - 6.204 voltage drop = 0.8 volts at MAF sensor wire
So there is something in that circuit before the MAF sensor that has a resistance value of 15510 ohms.... that's a lot.
7 volts source voltage
1990 ohms on burn off wire in sensor from terminal D to terminal A.
.8 volts / 1990 ohms = 0.0004 total amperage
7 volts / 0.0004 amps = 17500 total resistance
17500 total resistance - 1990 MAF sensor resistance = 15510 resistance left in the circuit
0.004 total amperage x 15510 unknown resistance = 6.204 voltage drop
7 volts - 6.204 voltage drop = 0.8 volts at MAF sensor wire
So there is something in that circuit before the MAF sensor that has a resistance value of 15510 ohms.... that's a lot.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
Hey guys, I have a 1985 Corvette and I'm having problems with the MAF sensor burn off function.
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
I went through the diagnostic test on All Data and my burn off module tested bad. I replaced it. My new one test good.
But here is the thing, on this diagnostic tree, where it says the following:
- Ground ALCL Terminal E
- Ignition 'ON' for 10 seconds
- Ignition 'OFF'
- Observe voltmeter within 4 seconds
- After 4 seconds the voltmeter should read greater than 2.5 volts for 1 second
When I test it with my multimeter, the highest voltage I get is 0.8 volts. When I test it with my power probe the highest voltage I get is 8 volts.
I tested the other module using both and the power probe didn't go above 2.5 volts, and the multimeter hit .3 volts.
So my power probe is picking up the voltage.
But now when I went to check to see if it was working inside the MAF, the wire doesn't glow.
All Data says this:
CHART C13, MAF BURN-OFF CHECK
Due to contaminates in the atmosphere a residue may build up on the air flow meters sensing wire. To maintain an accurate reading from the meter a "burn-off" cycle will occur if the ignition is turned off while in the closed loop mode and this is determined by the sate of the serial data line (CKT 461). If the engine is shut down while in open loop or the ignition is cycled on to off, the serial data line will be in a high state (about 5 volts) and remain there for about 5 seconds. However, if the ignition is turned off while in closed loop the serial data line will go to about 2.5 volts for 5 seconds. This voltage (2.5 volts or less) is what triggers the control circuitry in the burn off module and causes burn-off to occur.
When the conditions are met to activate burn-off, a 3 to 5 second delay will occur. After this delay the control circuitry will cause 12 volts to be applied on CKT 994 for 1 second and this will cause the meters sensing wire to glow red hot (about 1000°F) and the cycle is then complete.
A Code 33 or 34 will set if the airmeter fails and the same circuitry is used for MAF output as for burn off. Therefore the only functional check needed for the burn-off function is to check whether the burn-off signal is reaching the air meter after engine shutdown.
Optional test: To check burn-off disconnect MAF sensor front latches.
a. Ignition on.
b. Ground serial data line ALCL terminal E.
c. Ignition off and within 4 seconds observe MAF sensing wire. After about 4 seconds the wire should glow. If not ok, proceed with Chart.
1. In order for the burn-off cycle to function, the 12 volts on terminal E must remain until the burn-off signal occurs. This checks for the 12 volt shut down delay.
2. Grounding the ALCL terminal E causes the burn-off module to activate burnoff. This check will determine if the burn off module and wiring are OK.
My burnoff module passes the test so where do I go?
I removed the MAF sensor and bench tested the burn off function by applying 12 volts to terminal E on the sensor, 12 volts to terminal D on the sensor, and ground on terminal A on the sensor.
There was a very bright orange glow that was ridiculously obvious. Nothing happens when I follow the instructions to activate the burn off function on the car itself.
I don't really know where to go from here.
This has me stumped.
Any ideas? Thanks!
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39