p401 EGR issues (1 Viewer)
- Thread starter William839
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- check engine light egr fzj80 issues
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Either of the vacuum ports on the throttle body can be plugged and since they are vacuum ports all of the trash heads towards them for the most part. Fortunately the TB does not have to be removed to clean these ports out though I was only able to clean them by removing the small brass 90 degree tubes using pliers and a gentle pull and twist on them. Once you get the 90 degree tubes out a small bit of welding wire, cleaning spray or similar and you should be able to clear the ports and get debris out of the area.
I've also seen the tube that passes through the intake manifold from EGR to VSV get plugged but that would result in a PO402 not a PO401. Further, I've seen the VSV itself be plugged/clogged so that it never opens which would also cause a PO402 not a PO401. It's possible that other areas are also plugged.
First thing I would check with this system is the Vacuum modulator. Pop the cover off and look for contamination in the filter which indicates failure and replace the modulator if the filter is dirty to avoid dumping carbon into the system and causing other issues. If the modulator is clean but old I'd then run the FSM test on it before deciding to keep running it. After verifying the modulator you can work through testing the vac ports on the TB, testing the VSV and the EGR valve and hopefully find your problem in one of those areas. Wiring issues, a clogged passage in the intake or bad temp sensor, etc. could also cause a PO401 but I'd start with the other items first as they are easy to quickly check and are more likely to cause the code.
I've also seen the tube that passes through the intake manifold from EGR to VSV get plugged but that would result in a PO402 not a PO401. Further, I've seen the VSV itself be plugged/clogged so that it never opens which would also cause a PO402 not a PO401. It's possible that other areas are also plugged.
First thing I would check with this system is the Vacuum modulator. Pop the cover off and look for contamination in the filter which indicates failure and replace the modulator if the filter is dirty to avoid dumping carbon into the system and causing other issues. If the modulator is clean but old I'd then run the FSM test on it before deciding to keep running it. After verifying the modulator you can work through testing the vac ports on the TB, testing the VSV and the EGR valve and hopefully find your problem in one of those areas. Wiring issues, a clogged passage in the intake or bad temp sensor, etc. could also cause a PO401 but I'd start with the other items first as they are easy to quickly check and are more likely to cause the code.
This is a great diagram. It clearly depicts a question I am trying to resolve. Why is port P of the vacuum modulator connected to port E of the throttle body, why not port P of the throttle body? Also why is port P of the throttle body connected to the TVV?
The general schematic shows relatively simple connections. The diagram appears to represent the connections on my '97. I was trying to figure out if mine was not properly connected.
The general schematic shows relatively simple connections. The diagram appears to represent the connections on my '97. I was trying to figure out if mine was not properly connected.
Good thread. I have the P0401. 20k on rebuilt engine. Throttle body fully cleaned then. Plenum vacuum hose bypass. Silicone hoses. Have replaced modulator and vsv before this code and just replaced faulty egr but code coming back.
