After more than 400,000 miles on my '98 Jetta, the metal hoses to the EGR cooler finally cracked beyond repair. I removed them and blocked off the exhaust and the intake manifold ports with little plates of sheet metal, using the gaskets that were already there. I used VAG-COM to set channel 3 (EGR) to 33768. That's ok because I, uhhh, always drive my car off road.
Still, every once in a while I got a 1403 code, it was mad because it did not see a decrease in the MAF signal when it opened the EGR valve. It doesn't measure EGR directly, but it expects to see a decrease in the intake air when the EGR valve is open. What to do? I don't want to drive around the the check engine light on.
I obtained a vacuum switch, in my case an MPL 500 series, which might be obsolete. It really doesn't matter much what you use, as long as the contacts close when the vacuum that used to open the EGR valve is applied to its port. World Magnetics and Air Logic make similar switches, and you might find an automotive switch that would do the job. In any case, it shouldn't cost more than about $20 but it probably will.
I connected the switch in series with a 1000 ohm resistor between the MAF output signal and ground. Those connections are on the 6-pin connector at the MAF, but I don't remember which specific pins. If anybody has the service manual in front of him, maybe fill that in. I removed the vacuum hose from the old EGR valve and connected it to the vacuum switch.
I chose 1000 ohms because it seemed reasonable. With the engine off, key on, closing the switch changed the output voltage of the MAF from about .28 volts to about .26, or about 10%. I don't know how much the air flow is supposed to change when the EGR valve opens, but I figured 10% wasn't too radical. I haven't checked the voltage with the engine running, but things should stay proportional.
In any case, the check engine light hasn't come back on in about a week of driving, in conditions that normally would have turned it on. If I figure out somehow that I need the voltage to drop more than 10% when the ECU says the EGR valve should be open, I can replace the 1000 ohm resistor with a smaller value.
Still, every once in a while I got a 1403 code, it was mad because it did not see a decrease in the MAF signal when it opened the EGR valve. It doesn't measure EGR directly, but it expects to see a decrease in the intake air when the EGR valve is open. What to do? I don't want to drive around the the check engine light on.
I obtained a vacuum switch, in my case an MPL 500 series, which might be obsolete. It really doesn't matter much what you use, as long as the contacts close when the vacuum that used to open the EGR valve is applied to its port. World Magnetics and Air Logic make similar switches, and you might find an automotive switch that would do the job. In any case, it shouldn't cost more than about $20 but it probably will.
I connected the switch in series with a 1000 ohm resistor between the MAF output signal and ground. Those connections are on the 6-pin connector at the MAF, but I don't remember which specific pins. If anybody has the service manual in front of him, maybe fill that in. I removed the vacuum hose from the old EGR valve and connected it to the vacuum switch.
I chose 1000 ohms because it seemed reasonable. With the engine off, key on, closing the switch changed the output voltage of the MAF from about .28 volts to about .26, or about 10%. I don't know how much the air flow is supposed to change when the EGR valve opens, but I figured 10% wasn't too radical. I haven't checked the voltage with the engine running, but things should stay proportional.
In any case, the check engine light hasn't come back on in about a week of driving, in conditions that normally would have turned it on. If I figure out somehow that I need the voltage to drop more than 10% when the ECU says the EGR valve should be open, I can replace the 1000 ohm resistor with a smaller value.
