Code p0401 research. Vacuum question (1 Viewer)

[vegasfj40]

Hello everyone. Doing some checks per FSM and have a question I can't find. I am checking the vacuum lines from the throttle body to the modulator. One of them was crushed. However the R Port on the throttle body seems blocked. I put vacuum to the port with the engine off and it holds with no leaks. Is this correct? The E port is open.

 

[vegasfj40]

I also found the tube through the intake to be plugged solid. I ran another hose to bypass that for now. I think my throttle body needs to be taken off and cleaned. Ive checked the modulator per fsm and it passes, I replaced the VSV and vacuum lines.

 

[vegasfj40]

Just found my answer. Supposed to have no vacuum at idle and vacuum at 3500 rpm. Mine has no vacuum constant so appears the throttle body has to come off. I'll let everyone know if this cures my p0401 code . I haven't read about anyone having a port blockage at the throttle body.

 

[86tuning]

spray some carb cleaner into the port and some compressed air.
then again, r&r of the throttle isn't hard, but there's a coolant hose on the underside that's tricky to get to.

 

[86tuning]

i should remember what the EPR ports mean, but I cannot remember offhand. One is for evap. P is probably ported. R may be constant.

 

[vegasfj40]

Thanks for the reply. I did hit with some carb cleaner but haven't put compressed air to it. I'll try that when I get home. I've read dozens of threads about the p0401 code but haven't seen where a blockage in the port from the tbody can restrict vacuum to the modulator. Hopefully this is all.

 

[jatree]

Thanks for the reply. I did hit with some carb cleaner but haven't put compressed air to it. I'll try that when I get home. I've read dozens of threads about the p0401 code but haven't seen where a blockage in the port from the tbody can restrict vacuum to the modulator. Hopefully this is all.

Did this cure it? Gonna attempt to clear mine without removing TB for now. But no idea how plugged it is or whether the crud falling in is harmful.

Also, is it possible to do the intake-tube bypass to the VSV without removing the intake?

 

[vegasfj40]

Did this cure it? Gonna attempt to clear mine without removing TB for now. But no idea how plugged it is or whether the crud falling in is harmful.

Also, is it possible to do the intake-tube bypass to the VSV without removing the intake?

I actually had several blockages in the vacuum system. The port going through the intake was plugged so bad that I couldn't clear it so I bypassed with vacuum hose. Also had a blockage at the ports on of the throttle body. I had to remove the tbody to clean those. Also the VSV solenoid was leaking so I replaced that and the modulator. Since that was done I haven't had the code come back.

 

[vegasfj40]

I was able to replace the VSV without removing the intake by going underneath with a 3 ft long extension. There's a connection for the VSV at the front side of the intake that makes testing really easy.

 

[Hankg550]

I was able to replace the VSV without removing the intake by going underneath with a 3 ft long extension. There's a connection for the VSV at the front side of the intake that makes testing really easy.

Any pictures or instructions on how you got the vsv from underneath? I have the P0401 as well. Put in a new modulator valve cleared cel and it came back on immediately. Cleared one of the ports I read about where a member dropped a drill bit into. Mine was clear. Cleared cel after cleaning that port and the cel came back on again immediately.

 

[chap79]

Any pictures or instructions on how you got the vsv from underneath? I have the P0401 as well. Put in a new modulator valve cleared cel and it came back on immediately. Cleared one of the ports I read about where a member dropped a drill bit into. Mine was clear. Cleared cel after cleaning that port and the cel came back on again immediately.

Here's how I got to mine. Post #13
Builds - chap79's Build Thread

 

[Hankg550]

Thank you!

 

[jatree]

I actually had several blockages in the vacuum system. The port going through the intake was plugged so bad that I couldn't clear it so I bypassed with vacuum hose. Also had a blockage at the ports on of the throttle body. I had to remove the tbody to clean those. Also the VSV solenoid was leaking so I replaced that and the modulator. Since that was done I haven't had the code come back.

Ah I wonder which of your steps cleared the code. Any chance you did the vacuum test again after reassembling? I was able to clean both the ports today by removing the intake hose. But I'm still only getting good vacuum from the E/P (TB/VM) port and little to none on the R/R side even with a new hose.

I may just go ahead and take the VSV step even though mine is testing fine through the connector.

Here's how I got to mine. Post #13
Builds - chap79's Build Thread

Thank you!

 

[vegasfj40]

Code was cleared after the vacuum lines were cleared and the VSV was replaced. I replaced the modulator because I didn't want that to be a problem in the future. Did you put vacuum on the egr valve while engine is running to check it? Engine should stall or run rough when vacuum is applied. Do you have the FSM?

 

[jatree]

Yup have the FSM, have learned way more about Toyota EGR systems than I ever thought I would. I did put vacuum on the EGR while the engine was running. If I pinched the DS hose (to VSV), it stumbled quite easily when I pulled vacuum on the other side. However, it did not stumble when I didn't pinch the DS hose.

VSV connector is testing at 34 Ohms and I've done another test I read about here where I connected directly to it and verified I couldn't pull vacuum when the engine is cold.