EGR code P0402 (1 Viewer)

[Desertmedic80]

Greetings all. New Land Cruiser owner with an odd question. A little back story. I purchased a 1997 80 Series with 179,000 miles. Mostly original from the 3rd owner. Was in his family since 11,000 miles and 2 years old. Check engine light reveled a P0402 EGR Excessive flow code. (did not have the light when I purchased) I have driven it several hundred miles home and over the last week before getting the light. While checking the EGR with a hand vacuum I found someone at sometime had jammed a small ball bearing in the line coming off the EGR valve on the opposite side of the modulator. Has anyone ever seen that or know why anyone would do something like that. Engine runs fine Idols around 800 RPM and is smooth, acceleration is reasonable. I am a new owner but have driven many working overseas so I feel like it runs fine. Gas mileage is sinful as usual. I removed the suspect #0 piece of vacuum hose, removed the battery cable to reset the light and will test drive tomorrow. It started fine after the removal of the "hose bearing" If I get the light back where do I go from here?
Thanks in advance.

 

[enox]

Welcome to the forum.

Here, using the search function will greatly help you. This will get you started.

P0402 - Q&A

Experiencing P0402. I've decided that I don't want to do any of the workarounds, I want to fix it. Searched a lot of threads over the last few days. Here are some questions, need answers. Is the port from the EGR valve to the VSV clogged? - How can I determine this? I'm not sure how to...

forum.ih8mud.com

 

[saraujo]

Searching for this issue and EGR code you've listed, I've found the below previous thread and what it could be...

402, Shaking, rough idle, blinking CEL

Hello 1997 LX450 243K mileage. It has been throwing code 402 and intermittent rough idle, shaking on accelerating and sounds like my tail pipe is under water and my CEL starts to blink. If I disconnect battery or upon cold start there are no obvious issues. symptoms return after reaching temp...

forum.ih8mud.com

I believe the 96 and 97 are similar, so this should also apply, unless someone wants to correct me on this. Do you have an FSM? If not, I'd get one or I believe there's an electronic copy found here: Search results for query: FSM - https://forum.ih8mud.com/search/3469156/?q=FSM&t=resource&o=date

 

[Desertmedic80]

Thank you for the replies. I did get a FSM from the PO. I was just hoping that there was a common problem where I could start. Guess this will not be that simple. I will keep everyone updated as I go.

 

[Kay9Cop]

The bb is to disable the EGR system. No flow means the valve won’t open. It’s believed the hot exhaust gas contributes to the head gasket failure at the #6 cylinder. The EGR tube also melts the wiring harness at the back of the head.

 

[jpoole]

Where was the block exactly? If it was in the vacuum line running from the EGR valve to the intake manifold pass-through then the block was essentially disabling the VSV which means that the EGR valve could be opened at any time and that the VSV could not open and prevent the EGR from opening.

• That may not be clear but essentially vacuum from the throttle body will open the EGR valve.
• The vacuum modulator is in between the EGR Valve and the throttle body and helps determine when vacuum can get to the EGR valve and open it. Often the vacuum modulator can have issues which leads to a p0401 typically (insufficient flow).
• The VSV is on the other side of the vacuum circuit from the throttle body/vacuum modulator and is an electric valve that can be open or closed. This allows the computer to override the systems ability to build vacuum. If this fails open then vacuum can never build and you'll see p0401 codes. If this fails closes the vacuum can always build up (provided the modulator is a go) and you can get p0402s.

I assume that someone that only partially understands the system was hoping to resolve a p0401 by adding that block to the vacuum line after the EGR Valve, if that is indeed where the block was added. If that block was added at a different point it would have a different effect but a 402 is not an outcome in any other position I don't think.

The good thing if you got a 402 is that most of the system should be working. You'll need to test the VSV side of things to see if it's working properly as it may have issues (cracked/leaking lines or inability to close) that lead someone to add the block.

 

[Desertmedic80]

Where was the block exactly? If it was in the vacuum line running from the EGR valve to the intake manifold pass-through then the block was essentially disabling the VSV which means that the EGR valve could be opened at any time and that the VSV could not open and prevent the EGR from opening.

• That may not be clear but essentially vacuum from the throttle body will open the EGR valve.
• The vacuum modulator is in between the EGR Valve and the throttle body and helps determine when vacuum can get to the EGR valve and open it. Often the vacuum modulator can have issues which leads to a p0401 typically (insufficient flow).
• The VSV is on the other side of the vacuum circuit from the throttle body/vacuum modulator and is an electric valve that can be open or closed. This allows the computer to override the systems ability to build vacuum. If this fails open then vacuum can never build and you'll see p0401 codes. If this fails closes the vacuum can always build up (provided the modulator is a go) and you can get p0402s.

I assume that someone that only partially understands the system was hoping to resolve a p0401 by adding that block to the vacuum line after the EGR Valve, if that is indeed where the block was added. If that block was added at a different point it would have a different effect but a 402 is not an outcome in any other position I don't think.

The good thing if you got a 402 is that most of the system should be working. You'll need to test the VSV side of things to see if it's working properly as it may have issues (cracked/leaking lines or inability to close) that lead someone to add the block.

The BB was on the VSV side (which on my LC is mounted outside of the intake manifold) I have read that they were originally underneath and quite difficult to get to. I did "test" the VSV by putting power and ground to the terminals and hear and click. Before finding the BB, I removed and blew out (with compressed air as well as carb and choke cleaner) both lines from the manifold to the vacuum modulator. They both seems quite clogged initially. I drove around today getting up to operating temp, around town and high way and have not got the light to come back on. I does seem to idol about a 100 rpms less but might have a slight stumble now. I am thinking I might still have some problems/blockages/leaks somewhere in the system. I still have to test the vacuum modulator but will do that once the engine cools off a little.

 

[Desertmedic80]

Ok so this is where I stand. EGR, modulator, VSV all test fine. I replaced every line that even looked like it could be bad. Idol is around 900 when warm. Light stayed out for about 2 days and came back on. Just out of perverse curiosity I rescanned and it is now showing to be a P0401 not 402 like it was. Any suggestions are greatly appreciated.

 

[jpoole]

As I understand it you previously had a block in the line just past the egr valve, or on the other side of the egr valve from the throttle body. This was eliminating the vsv valve and any leaks that may be between it and the egr valve from the system. At that point you got a 402, I assume because the computer couldn't open air flow at the VSV and disable the egr valve from opening.

Now, with that blockage removed you get a 401 which means vacuum is not building correctly. I'm tempted to focus on the fact that you removed the blockage which would point to problems in the vsv valve or the lines from the egr valve to the vsv. Could be an electrical or a vacuum leak type of problem. I'd start there.

It's also possible that you aren't getting good vacuum into the system or through the modulator but that wouldn't have allowed the 402. In any case you can place a vacuum gauge inline with the system at different points from throttle body to vsv to test each part of the system. Blocking off the upstream stuff (away from the throttle body or vacuum source) can allow you to isolate and just test the downstream stuff to that point.

Buy a vacuum gauge, t fitting, etc. and start testing the vacuum system from the TB and through the system and you should find your problem unless it's intermittent and hard to duplicate.

 

[Desertmedic80]

Thank you for all the responses first of all. Sorry for the delay in updating second. After following the advice here (Thank you all) and testing procedures in the FSM I have got the light to go out and stay out. What I did to fix it I'm not completely sure. I replaced several hoses that were obviously bad or I questioned. Cleaned and blew out the vacuum modulator. Carb cleaner and compressed air the ports on the intake and reversed the hoses on the VSV valve. Not sure if the last one had anything to do with squat but the FSM showed that the PO or the last person to mess with it reversed them. It is mounted outside the intake so at some point it has been replaced. Either way it is out and has stayed out for over a week with daily driving so I am guessing that I got lucky and stumbled across what was causing it.