Greetings,

96 LS400 252K

Had P0401 Insufficient EGR flow for a while now. Some have fixed this with a 10K Ohm resistor at the EGR Temp Sensor, but I'm not sure if this is the same thing as the flow sensor, and if this is the connector at the top of the engine LHS, which is a 6-pin connector as shown in the pic.

Does anyone have specific directions here as to which wires or pins are used. (This the right connector, isn't it?)

Thanks a bunch - inspection is July so have some time.

Edit: Fixed - see page 2 of this thread.

 

why don't you fix it... it probably just needs to be cleaned as EGRs get chock full of carbon. they don't negatively affect performance and in fact play a large role in keeping EGT temps down.

 

I've researched this quite a bit and i agree with PD - it's better for your engine to keep the EGR functional due to the lower EGT temps (not to mention that you're producing less smog in the environment). Also, since our EGR is modulated according to engine load (i.e. it's not a simple on/off system like early EGR's), it actually helps fuel economy.

 

Ok the current situation is the EGR pipe broke in half, and I blanked off the two openings. Shortly after that, I got the code, which is annoying but makes sense.

I've tried replacing the pipe but it's a real PITA and I've been unable to reach where I have to without either taking off the exhaust or the intake. The general advise in this situation is to delete the sensor (the EGR system is not even used in Japan).

 

the EGR isnt used in japan because it costs MONEY and as it's not required for their emissions laws toyota would be spending money it didnt need to.

 

I hear ya, and you are right about doing it properly being better. But for a car this old with this many miles, if I can get just a bit more out of it before it dies or I just move on to another LS, then I'd be content. People do successfully delete this sensor and get rid the engine code, which is what you need for inspection here in NJ.

There is confusion in many of the threads about this, and so if I can get this fixed I will post up with details and pics. In some vehicles, the EGR gas temp sensor is sticking out of the EGR pipe just as it enters the rear of the air intake. In my LS, it appears to be on the EGR valve itself, on the side of the intake, at least according to the manual. I've disconnected the sensor plug and will put in the resistor as soon as it arrives.

So question: does the temp sensor determine the gas flow rate, something like MAF sensor?

 

Any updates?

 

No, the gas temp sensor does not determine anything. It's only function is to read the temp of the gas. The ECM will throw a code 71 if the gas temp sensor does not indicate a rise in temperature when the EGR is supposed to be operating.

 

How does a fixed ohm resistor help then? (It hasn't, btw, I must be getting this wrong). Also code 71 is for the 96 or is that for older obd1?

 

Yes, sorry, the code 71 is for OBD-I, but it corresponds to your P0401. The fixed resistor works because it fakes the ECM into thinking that the EGR gas is at the correct temperature, and so it is satisfied that the EGR is working and will not throw a code.

 

Ok so I've got 40+ miles since I put in the resistor, and still the code is present. Do you have any recommendations? There won't appear to be any actual change in temp, if the resistor is fixed at 10K ohms. On some other threads on the SC, there is a temp sensor that goes into the EGR pipe where it enters the engine, a bit like an O2 sensor. Must work different in this case.

 

Did you clear the error code after putting the resistor in?

 

Nope, error code still there. I assume this is not the right fix. I will look at the problem again this Sunday.

 

What I meant is, did you clear the error code using a scan tool after you made the fix?

 

Nope - I assumed it would go out by itself. It has done according to other threads. I've done 50+ miles since.