P0234 error code

[trannyheap]

Hi Gents. My mk7 tranny continually throws up a P0234 error code, turbo overboost condition. The turbo actuator is working ok, you can see it moving when the engine is revved, but the error code keeps re-appearing. I don't know if this is connected or a different issue, but often it takes considerable cranking over to start when the engine is hot. The starting problem is annoying, but the turbo problem is worrying. Any ideas?

[trannyheap]

Sorry, should have mentioned, it's a 2.4 RWD 140ps

[knobby1]

Sorry, should have mentioned, it's a 2.4 RWD 140ps

Some time ago I had the overboost/underboost codes a few times on my RWD 140 too, I cleared them but they quickly returned a day or so later....turned out to be a duff EGR. You'll often get this code and possibly a couple of others if you blank the EGR as well.

If the EGR valve is stuck/sticking closed, the "overboost" code often comes up and they can become a pig to start....The EGR is normally open during start & at low rpm/throttle settings, then it progressively closes as the throttle setting, rpm and load increases. Can you hear the EGR doing the "self clean" thing when you turn the engine off..?? Sounds like a small hack saw in the engine bay for a few seconds.

If the EGR is doing the sticking "open & closed" thing you'll sometimes get both the overboost/underboost codes, often accompanied by a faulty EGR code. If you have a decent code reader you can do "Live read-outs" and can see what the EGR is doing whilst driving, it shows as a percentage.

Might pay to remove and clean your MAP sensor too, they get all clogged up with spooge. The MAF/IAT sensor seems to stay reasonably clean most of the time as it's upstream of the crankcase breather inlet hose.

Lord Knobrot

[trannyheap]

Hi. The EGR was removed, blanked off and the brain re-mapped, so it doesn't know it should have one. I've just renewed the MAP sensor as the fault code for that was also coming up on my local garage's reader, although not mine. The van runs perfectly, although a bit heavy on the juice, apart from the starting issue. I've found if I let the glow plugs heat up before trying to start the engine it starts easier, but that shouldn't be necessary on a hot engine. I'm concerned about the engine management light being permanently on in-case something serious occurs and I don't know about it.

[knobby1]

Hi. The EGR was removed, blanked off and the brain re-mapped, so it doesn't know it should have one. I've just renewed the MAP sensor as the fault code for that was also coming up on my local garage's reader, although not mine. The van runs perfectly, although a bit heavy on the juice, apart from the starting issue. I've found if I let the glow plugs heat up before trying to start the engine it starts easier, but that shouldn't be necessary on a hot engine. I'm concerned about the engine management light being permanently on in-case something serious occurs and I don't know about it.

If the EGR has been removed/blanked and mapped out, that's fine....however, if the PCM remap hasn't been completely modified to suit, the MAP sensor won't know the EGR isn't there and the higher manifold pressure at certain settings will be detected by the MAP sensor and hence throw up a fault....as you have discovered. The PCM is expecting to see certain pressures at certain rpms, loads and throttle settings, if it's not within the PCM's specified range, it'll throw up a fault code.

I found I had more running/starting issues with my EGR blanked off than when it was fitted and working as designed.

If you're in the UK, you may have MOT issues in the future if your EGR is blanked, mapped out or missing....I understand they'll be checking for correct operation of these items etc... Same goes for DPF's on Euro-5 machines. As I understand it, if they're fitted as standard, they must be there and work as designed or you'll go back home with a fail.

[karl]

Sorry, should have mentioned, it's a 2.4 RWD 140ps

Some time ago I had the overboost/underboost codes a few times on my RWD 140 too, I cleared them but they quickly returned a day or so later....turned out to be a duff EGR. You'll often get this code and possibly a couple of others if you blank the EGR as well.

If the EGR valve is stuck/sticking closed, the "overboost" code often comes up and they can become a pig to start....The EGR is normally open during start & at low rpm/throttle settings, then it progressively closes as the throttle setting, rpm and load increases. Can you hear the EGR doing the "self clean" thing when you turn the engine off..?? Sounds like a small hack saw in the engine bay for a few seconds.

If the EGR is doing the sticking "open & closed" thing you'll sometimes get both the overboost/underboost codes, often accompanied by a faulty EGR code. If you have a decent code reader you can do "Live read-outs" and can see what the EGR is doing whilst driving, it shows as a percentage.

Might pay to remove and clean your MAP sensor too, they get all clogged up with spooge. The MAF/IAT sensor seems to stay reasonably clean most of the time as it's upstream of the crankcase breather inlet hose.

Lord Knobrot

+1 had this a few time now even none startering van because of the egr valve.had one yestarday on a fiesta van and that was the egr valve