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Underbody braces, turbos and more!

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PostPosted: Thu Sep 03, 2009 11:40 am 
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Joined: Sun Aug 30, 2009 6:24 pm
Posts: 14
Location: Vancouver
I have been trying to isolate a DTC 51 and know from reading a (Suzuki Swift?) FSM - DTC 51 excerpt (supplied here at TeamSwift by KoeGeo) that DTC 51 will set if:
-"System is operating in Closed Loop operation."
-"Difference of MAP sensor between EGR SV valve is 'ON' and when 'OFF' is less than a calibrated value."
I found a MAP sensor test procedure at ARRC online:

TESTING
1. Turn the key to the ON position but do not start the vehicle.
2. Backprobe the signal wire of the sensor. --> I determined this to be the center wire of the three-wire connector, orange with a black stripe - am I correct?
3. Connect a DMM to the sensor and a known good ground.
4. The voltage should be 4v to 5v. --> I got 3.63v
5. Start the vehicle, the reading should be 1.1v to 1.3v. --> I got 1.70 to 1.75v (voltage reading fluctuates a little)
6. Replace the sensor as needed.

So, what exactly is Closed Loop operation? Would I have any control over this?

And, would my voltage readings in step 4. & 5. be out of range enough to warrant replacement of the MAP sensor? If KoeGeo reads this, could you check the FSM for me to see what voltages are called for in steps 4. & 5. please?
Thanks, FFF


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PostPosted: Thu Sep 03, 2009 4:08 pm 
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Joined: Sat Apr 24, 2004 9:48 am
Posts: 725
Location: Winnipeg
While my experience is with the newer ECU's, orange black sounds like correct wire...voltage for engine off sounds about right, voltage engine running would lead me to think that your engine idles with lower than normal vacume. I think that code is pointing you toward an EGR, or engine vacume problem, and not with the map sensor itself...trying another sensor can never hurt though...especially if you don't find anything obvious with the EGR.


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PostPosted: Thu Sep 03, 2009 6:14 pm 
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Joined: Tue Feb 10, 2009 4:09 pm
Posts: 238
Location: Brinkworth, UK
I think thats an EGR problem. The ECU detects EGR opening by looking for a drop in manifold pressure. Time to pull the EGR and clean out all the passages, check the hoses for vacuum leaks too. Closed loop operation is when the ECU is using the O2 sensor to keep the fuelling correct, this implies that the conditions for closed loop operation are the same as those for EGR operation. Closed loop operation usually happens when the vehicle is at normal operating temperature and over a certain speed, the ECU reverts to open loop operation (not using O2 sensor) when above something like 75% throttle.


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PostPosted: Fri Sep 04, 2009 5:43 pm 
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Joined: Sun Aug 30, 2009 6:24 pm
Posts: 14
Location: Vancouver
Mr. Pipe ... thanks for confirmation on the MAP sensor signal wire colour ... I'm only aware of one suitable wreck in my area to check for a used MAP sensor ... I'll see if it's still there or not, however, these Ralph's guys still want a lot of money for this kind of thing and the only way to bargain them down is by taking the thing as is - no refunds. I think I'll exhaust my EGR valve intake passage cleaning options and re-test before shelling out for a MAP sensor.

Rhinoman ... thanks for the good info on Closed / Open Loop operation ... I read and re-read what you said about "this implies that the conditions for closed loop operation are the same as those for EGR operation" ... so ... O2 sensor usage by the ECU and EGR operation are parallel but not directly related functions based on like 'conditions'? Have I got that right?


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PostPosted: Sun Sep 06, 2009 11:21 am 
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Joined: Tue Feb 10, 2009 4:09 pm
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Location: Brinkworth, UK
The O2 sensor works over a fairly narrow temperature range so its switched out at idle and above something like 75% throttle, it is used to determine that the Air Fuel Ratiois correct. The EGR allows a small amount of exhaust gasses into the combustion chamber to improve part throttle efficiency, its shut at idle and at higher loads. They are very different functions but the same status flags could well be used to determine operation.


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PostPosted: Fri Sep 11, 2009 9:53 pm 
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Joined: Sun Aug 30, 2009 6:24 pm
Posts: 14
Location: Vancouver
Well ... I removed the EGR valve today and cleaned it up. I cleaned / blew out the intake manifold passages to the extent that I could still assembled ... pretty sooty in there - lots of good clean fun.
After re-assembly and a short test drive ... no CEL/MIL ... but it's a little too soon to draw a conclusion of DTC 51 resolved just yet.

One thing I found puzzling, I was unable to force pressurized air through the longer EGR passage at the aft end of the intake manifold - can anyone say if this passage is also valve-controlled somehow ... or ... is it simply (still) plugged with soot?


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PostPosted: Sat Sep 12, 2009 4:12 am 
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Joined: Thu Jul 20, 2006 7:17 pm
Posts: 1405
Location: Alberta, Canada
its still plugged. Its tough to get the last little bit out on the throttle body end. Poke at it from both sides until the passage is clear. Have done quite a few for this issue lately. Its a bit of a pain, but doens't require any parts which is handy.

_________________
1995 Swift w/16V 4.39s, 3tech cam, Esteem t-body, Header, needs more.
1995 Gt Mustang "Boss Shinoda" package.
1999 F150 4x4 Supercharged
1967 Mustang 428 auto, never ending expensive project
1993 Civic si h22a, fell in my lap, couldn't resist!


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PostPosted: Sat Sep 12, 2009 11:01 am 
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Joined: Sun Aug 30, 2009 6:24 pm
Posts: 14
Location: Vancouver
Uhhh ... thanks for that codyb76 ... that's what I was afraid of ...

So, what all do I have to remove to get at the other end of the passage - air cleaner assembly obviously and throttle body? and ... ?

Thanks, FFF


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PostPosted: Sat Sep 12, 2009 9:18 pm 
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Joined: Thu Jul 20, 2006 7:17 pm
Posts: 1405
Location: Alberta, Canada
throttle body. dont sweat it, its not tough at all to get off.

_________________
1995 Swift w/16V 4.39s, 3tech cam, Esteem t-body, Header, needs more.
1995 Gt Mustang "Boss Shinoda" package.
1999 F150 4x4 Supercharged
1967 Mustang 428 auto, never ending expensive project
1993 Civic si h22a, fell in my lap, couldn't resist!


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