Diagnostics recommendation
Discussion
Our Mazda 5 may well have a failing DPF (has required more than one forced regeneration) but I'd like to actually get to the bottom of the issue which may be sensor related too and there is some uneveness in the running of the vehicle at specific speeds.
Can anyone therefore recommend a diagnostics firm in Herts/Beds/North London etc? Ideally, they could also do a rolling road or road test with diagnostics plugged in too
Can anyone therefore recommend a diagnostics firm in Herts/Beds/North London etc? Ideally, they could also do a rolling road or road test with diagnostics plugged in too
2.0??
If so, the most common causes are...
1) a sticking EGR valve - most common problem by far (more often than not throws up codes for the MAF sensor due to the way EGR flow is monitored) also the most commonly misdiagnosed. Don't let anyone tell you it needs replacing, as they can be stripped and cleaned, after which, they operate perfectly. Could also be the cause of the rough running, as if it's stuck open but the PCM thinks it's closed, it is essentially unmetered air. A couple of hours labour tops to fix.
2) injectors that are out of spec. Ask for the injector learn values, both before and after a learn cycle has been performed. Any value outside of +100 or - 100 indicates a problem.
Just because the DPF has had to be manually regenerated a few times, it doesn't mean it will need replacement.
What you need to remember is that a DPF is just essentially a storage unit, nothing more, nothing less - they don't really fail, as there isn't really anything to fail. A DPF with more than 15g/l does require replacement, but only because above this, they produce too much heat during a regeneration and the core can be damaged.
99/100 are replaced incorrectly, as it's something else in the system causing normal regeneration to fail or be incomplete (see above)
If so, the most common causes are...
1) a sticking EGR valve - most common problem by far (more often than not throws up codes for the MAF sensor due to the way EGR flow is monitored) also the most commonly misdiagnosed. Don't let anyone tell you it needs replacing, as they can be stripped and cleaned, after which, they operate perfectly. Could also be the cause of the rough running, as if it's stuck open but the PCM thinks it's closed, it is essentially unmetered air. A couple of hours labour tops to fix.
2) injectors that are out of spec. Ask for the injector learn values, both before and after a learn cycle has been performed. Any value outside of +100 or - 100 indicates a problem.
Just because the DPF has had to be manually regenerated a few times, it doesn't mean it will need replacement.
What you need to remember is that a DPF is just essentially a storage unit, nothing more, nothing less - they don't really fail, as there isn't really anything to fail. A DPF with more than 15g/l does require replacement, but only because above this, they produce too much heat during a regeneration and the core can be damaged.
99/100 are replaced incorrectly, as it's something else in the system causing normal regeneration to fail or be incomplete (see above)
Superhoop said:
2.0??
Yes, 2.0l SportMany thanks for all the additional info too. The car went into limp mode 2 weeks ago in Wales and a regen was done then (DPF,TCS lights etc) but those have returned 900 miles later. It was replaced 2 years ago too when we had issues when travelling through France so had no real choice at the time other than the Mazda dealer to which we were recovered.
Definitely will investigate all - certainly the MAF has been stated as the possible issue when the last diagnostics were done a couple of months ago. So definitely interesting what you say about the EGR valve.
Will try to get someone to do the injector readings
Thanks again
Don't worry about the TCS light, it will be fault code C1119 - this pings up in the system with a number of engine management fault codes and will simply clear when the engine related codes are rectified - the most common code for throwing up C1119?? P0101, P0104 or both
These are both MAF codes and will be caused by the EGR valve sticking open.
These are both MAF codes and will be caused by the EGR valve sticking open.
Superhoop said:
Don't worry about the TCS light, it will be fault code C1119 - this pings up in the system with a number of engine management fault codes and will simply clear when the engine related codes are rectified - the most common code for throwing up C1119?? P0101, P0104 or both
These are both MAF codes and will be caused by the EGR valve sticking open.
Interesting These are both MAF codes and will be caused by the EGR valve sticking open.
I'll check the paperwork in a mo and see what codes were reported in Wales. Sensibly they gave us them when doing the regen Qwert1e said:
Why not go to the local dealer and book your car in for "diagnostics only"?
as per above - they have stated MAF (despite previously being replaced <12k ago) and it has been cleaned etc. Car running hasn't been faultless despite the original replacement. I'm also not particularly keen to use either 'local dealer' again following previous experience with their workWhy not try a Mazda 5 owners forum .Most of these forums have some maker techs posting, so you might get some advice on problem. I did a google and came up with a few.Such as
http://www.mazdas247.com/forum/forumdisplay.php?19...
http://www.mazdas247.com/forum/forumdisplay.php?19...
P0102 & P0104 are MAF sensor codes. These are set due to the way the PCM (ECU) monitors EGR flow, the short(ish) version of which is:
the EGR valve is pushed open by a PCM controlled stepper motor, which holds it open. To close the EGR valve, the PCM just winds the stepper motor back, but the valve itself (mechanical) is closed by spring pressure. The PCM only monitors the position of the stepper motor.
When the PCM opens the EGR valve, it expects to see a drop in MAF as it has just introduced air from another source (the EGR valve), when it closes the EGR valve, it expects MAF to rise again, as it has taken away the additional source of airflow.
All fine in principal, however, if the EGR valve is sticking due to carbon build up, the mechanical part of the valve stays open against spring pressure although the stepper motor closes - The PCM however thinks the EGR valve is shut, because it has seen the stepper motor position change - As a result, it doesn't see the MAF change as expected, so flags a MAF sensor fault code. In this case P0102 & P0104 - simple really!!
How does this lead to the DPF issue?
Again simple really. When the PCM determines a regen is required it does three things
1) closely controls turbo vane angle - this makes the turbo work harder and generates heat
2) instigates post injections of fuel - this raises the temperature of the catalyst (mounted in the DPF unit in front of the DPF itself)
3) It closes the EGR valve - recycling exhaust gas when you're trying to regen isn't ideal.
So you have two problems really, but both the same primary cause. With the EGR valve open when it shouldn't be, the engine produces particulate matter (PM) quicker than it should, leading to more regenerations being required, and as the EGR valve is open during a regeneration, it is only ever partially effective.
Removing, stripping, cleaning, rebuilding of the EGR valve, followed by a regeneration will sort 4 of the 5 codes you have present (P0102, P0104, P2458 and P242F). The other code, P0045 may just be a glitch due to exhaust restriction due to the DPF being partially blocked/restricted. The biggest concern would be what the current PM volume is, as anything over 15g/l means it won't allow a manual regeneration to take place.
the EGR valve is pushed open by a PCM controlled stepper motor, which holds it open. To close the EGR valve, the PCM just winds the stepper motor back, but the valve itself (mechanical) is closed by spring pressure. The PCM only monitors the position of the stepper motor.
When the PCM opens the EGR valve, it expects to see a drop in MAF as it has just introduced air from another source (the EGR valve), when it closes the EGR valve, it expects MAF to rise again, as it has taken away the additional source of airflow.
All fine in principal, however, if the EGR valve is sticking due to carbon build up, the mechanical part of the valve stays open against spring pressure although the stepper motor closes - The PCM however thinks the EGR valve is shut, because it has seen the stepper motor position change - As a result, it doesn't see the MAF change as expected, so flags a MAF sensor fault code. In this case P0102 & P0104 - simple really!!
How does this lead to the DPF issue?
Again simple really. When the PCM determines a regen is required it does three things
1) closely controls turbo vane angle - this makes the turbo work harder and generates heat
2) instigates post injections of fuel - this raises the temperature of the catalyst (mounted in the DPF unit in front of the DPF itself)
3) It closes the EGR valve - recycling exhaust gas when you're trying to regen isn't ideal.
So you have two problems really, but both the same primary cause. With the EGR valve open when it shouldn't be, the engine produces particulate matter (PM) quicker than it should, leading to more regenerations being required, and as the EGR valve is open during a regeneration, it is only ever partially effective.
Removing, stripping, cleaning, rebuilding of the EGR valve, followed by a regeneration will sort 4 of the 5 codes you have present (P0102, P0104, P2458 and P242F). The other code, P0045 may just be a glitch due to exhaust restriction due to the DPF being partially blocked/restricted. The biggest concern would be what the current PM volume is, as anything over 15g/l means it won't allow a manual regeneration to take place.
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