11 replies to this topic

[G-Bob]

Right, less fluffy forum crap and gonnae help me with my engine! Just found what code it's spitting out and it's a P0404 which is a throttle related. I've reset the code just now but I'm not sure how long it'll last. Is this an EGR related problem or something to do with the throttle body? Where is the EGR sensor and could it be loose/needing a clean? I have a spare throttle body and can fit that if it's causing it. Any help appreciated. Bob

[techieboy]

Could be the old connector/loom of doom issue with the wiring loom in the nearside rear wheel arch. The wiring connectors might need cleaning up and reconnecting properly.

[chris_uk]

What does that mean?

The EGR (Exhaust Gas Recirculation) system's purpose is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert, it displaces oxygen and fuel, thereby lowering cylinder temps, which, in turn, lowers oxides of nitrogen emissions. For that reason it needs to be carefully metered into the cylinders (via the EGR valve) so as not to adversely affect the engine's performance. (Too much EGR and the engine won't idle). you have a P0404, then the EGR valve is likely an electrically controlled EGR valve instead of a vacuum controlled EGR valve. Also, the valve will usually have a feedback system built into it that informs the PCM (Powertrain Control Module) what position the valve is in; open, closed, or somewhere in between. The PCM needs to know this to determine whether or not the valve is operating as needed. If the PCM determines that the valve should be operating, but the feedback circuit shows that the valve is not open, this code will set. Or if the PCM determines the valve should be closed but the feedback signal indicates that the valve is open, this code will set.

Symptoms

There may be no symptoms of a P0404 DTC other than the MIL (malfunction indicator lamp) or check engine light. However, Exhaust Gas Recirculation systems are inherently problematic due to carbon buildup in the intake manifold, etc. This normal buildup can lodge in an EGR valve, holding it open when it should be closed. If this is the case, the engine may idle rough, or not at all. If the valve has failed and is NOT opening, then symptoms would be higher combustion temps and as a result, higher Nox emissions. But the latter symptoms aren't going to be noticeable to a driver.

Causes

Usually this code points to either carbon buildup or a bad EGR valve. However that doesn't rule out the following:

Open or short in the 5 Volt reference circuit
Open or short in the ground circuit
Open or short in the PCM controlled voltage circuit
Bad PCM (less likely)

Possible Solutions

Using a scan tool command the EGR valve to open while watching the actual EGR position (it will probably be labeled "desired EGR" or something similar). The actual EGR position should be very close to the "desired" EGR position. If it is, then the problem is likely intermittent. It may have been a lodged piece of carbon that has since dislodged, or it could be a bad EGR valve winding that intermittently opens or shorts as the valve temperature changes.
If the EGR "desired" position is not close to the "actual" position, then unplug the EGR sensor. Check for a good 5 Volt reference voltage to the connector. If it doesn't show a reference voltage, repair an open or short in the 5 Volt reference circuit.
If there is a 5 volt reference voltage, activate the EGR with the scanner, monitor the EGR ground circuit with a DVOM (Digital Volt/Ohm meter). It should indicate a good ground. If it doesn't then repair the ground circuit.
If there is a good ground, then check the control circuit. It should indicate voltage that varies according to the percentage that the EGR is open. As it's open more, the voltage should increase accordingly. If it does, then replace the EGR valve. If the voltage doesn't increase incrementally, then repair open or short in EGR control circuit.

[G-Bob]

Nearside wheel arch? Front or Back?

[chris_uk]

Nearside wheel arch? Front or Back?

he said rear

[G-Bob]

What does that mean?

The EGR (Exhaust Gas Recirculation) system's purpose is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert, it displaces oxygen and fuel, thereby lowering cylinder temps, which, in turn, lowers oxides of nitrogen emissions. For that reason it needs to be carefully metered into the cylinders (via the EGR valve) so as not to adversely affect the engine's performance. (Too much EGR and the engine won't idle). you have a P0404, then the EGR valve is likely an electrically controlled EGR valve instead of a vacuum controlled EGR valve. Also, the valve will usually have a feedback system built into it that informs the PCM (Powertrain Control Module) what position the valve is in; open, closed, or somewhere in between. The PCM needs to know this to determine whether or not the valve is operating as needed. If the PCM determines that the valve should be operating, but the feedback circuit shows that the valve is not open, this code will set. Or if the PCM determines the valve should be closed but the feedback signal indicates that the valve is open, this code will set.

Symptoms

There may be no symptoms of a P0404 DTC other than the MIL (malfunction indicator lamp) or check engine light. However, Exhaust Gas Recirculation systems are inherently problematic due to carbon buildup in the intake manifold, etc. This normal buildup can lodge in an EGR valve, holding it open when it should be closed. If this is the case, the engine may idle rough, or not at all. If the valve has failed and is NOT opening, then symptoms would be higher combustion temps and as a result, higher Nox emissions. But the latter symptoms aren't going to be noticeable to a driver.

Causes

Usually this code points to either carbon buildup or a bad EGR valve. However that doesn't rule out the following:

Open or short in the 5 Volt reference circuit
Open or short in the ground circuit
Open or short in the PCM controlled voltage circuit
Bad PCM (less likely)

Possible Solutions

Using a scan tool command the EGR valve to open while watching the actual EGR position (it will probably be labeled "desired EGR" or something similar). The actual EGR position should be very close to the "desired" EGR position. If it is, then the problem is likely intermittent. It may have been a lodged piece of carbon that has since dislodged, or it could be a bad EGR valve winding that intermittently opens or shorts as the valve temperature changes.
If the EGR "desired" position is not close to the "actual" position, then unplug the EGR sensor. Check for a good 5 Volt reference voltage to the connector. If it doesn't show a reference voltage, repair an open or short in the 5 Volt reference circuit.
If there is a 5 volt reference voltage, activate the EGR with the scanner, monitor the EGR ground circuit with a DVOM (Digital Volt/Ohm meter). It should indicate a good ground. If it doesn't then repair the ground circuit.
If there is a good ground, then check the control circuit. It should indicate voltage that varies according to the percentage that the EGR is open. As it's open more, the voltage should increase accordingly. If it does, then replace the EGR valve. If the voltage doesn't increase incrementally, then repair open or short in EGR control circuit.

That's good info.

I was using the ODB2 thing to activate the Throttle and it seems to change the voltages dramatically when I when I was doing it.

See when they are talking about carbom build up, is that on the sensor or on the throttlebody?

[chris_uk]

i think they are talking about the EGR valve, you would have to take it off to see it tho.

[greasemonkey]

just checked on tis 2 web the code is (Exhaust Gas Recirculation Circuit Range/Performance (Open Valve)) if you want vauxhalls checking procedures ill email them to you, but im betting egr valve faulty. most common component i replace on the full range of vauxhalls.

[techieboy]

Yep, definitely sounds like the EGR valve given the explanation of the error code. Easy enough to check by blanking off the EGR hole in the cylinder block and moving the EGR valve out of the way. You can run it like that or get rid of the whole thing and fit a little electronic cheater to convince the engine it's still there and working. You can get that from Vocky, via the Z22SE website shop.

[G-Bob]

Yep, definitely sounds like the EGR valve given the explanation of the error code.

Easy enough to check by blanking off the EGR hole in the cylinder block and moving the EGR valve out of the way. You can run it like that or get rid of the whole thing and fit a little electronic cheater to convince the engine it's still there and working. You can get that from Vocky, via the Z22SE website shop.

I have an EGR cheater which I got ages ago for fitting with my 2.4 inlet but I've never got round to fitting it.

Just went out and ran the car for a little while after resetting the codes and it's running smooth as you like, but for how long I don't know.

There was another code that appeared too, a P1523 or something like that. it was 1500 and something anyway. Looking on z22se it looks like people get this one too if the EGR is playing up.

[G-Bob]

just checked on tis 2 web the code is (Exhaust Gas Recirculation Circuit Range/Performance (Open Valve))
if you want vauxhalls checking procedures ill email them to you, but im betting egr valve faulty. most common component i replace on the full range of vauxhalls.

If you have them that would be great.

Bob@bobtog.tk

[greasemonkey]

give it a drive and see what code returns, all the 15-- codes are related to the electronic throttle body. guess if the engine is struggling and trying to stall due to faulty/sticing egr vale it could store this code.