2003 mazda tribute p0403

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#1
2003 Mazda tribute esv6 3.0

P0403 DTC

Ran testing on erg, dpfe sensor & vac regulator

Components test ok
Still not getting vac to egr throws p0403

I am going to check for resistance between vac regulator & pcm wire as well as wire from dpfe sensor.
If it is the pcm. Can I install a flashed pcm & will I need to reprogram keys.

Is the pats procedure something I can do? Can a reputable auto repair shop to this? Or is this a dealer only procedure.

Thank you in advance

T99m
 
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#2
Replqacing the PCM is jumping the gun I think, I will pull up a wiring diagram give a quick look -
to dbl check-
No other codes? no recient repairs? everything work? - making sure PCM will command EGR.
Do you have 12v at EGR vacuum regulator solenoid?
Is there vacuum to solenoid?
 
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#5
Again I ask - no other codes, everything works, speedo, ECT - vehicle reaches @195degrees,
You have 5v, at DPFS , good ground?

Without a scanner to command EGR lets try to create conditions for PCM to command EGR. use a vacuum gauge to EGR valve side of solenoid- you will need to snake the line out under hood to observe. The PCM needs to see speed to command EGR - so you will need to drive car...

SORRY GTG
 
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#6
Kev

Everything works. Reaches 195 good ground & 5v at dpfe sensor
No vacuum from regulator when accelerating. Gauge connected.

Vehicle actually runs good

190,000 miles well maintained
 
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#7
Basically the PCM grounds the solenoid - sends vacuum to EGR valve -
So is there 12v on both sides of solenoid?
did you try checking that solenoid operates? opens when grounded- isn't that a Vio colored wire?
with 12v to solenoid grunding the other will solenoid open sending vac to egr?

then we will need to check the wire from EGR solenoid to PCM - is it open ?
 
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#8
Kev

I do have 12v on both terminals on the reg. Can I use a test light to pcm vt wire to simulate pcm signal to check if reg with allow vacuum through? Do know where I can find pcm pin out diagram? I believe it is pin#17 to the reg.
 
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#9
We can unplug harness - overly cautious of PCM... and jump 12v and ground to the solenoid see if solenoid opens, sends vac to EGR..
then if it works it would be checking the pin out of PCM... fingers crossed its the solenoid
 
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#10
Kev

Let me understand your direction. I should disconnect terminal connection at reg & apply 12v to power side of the reg
Ground other terminal. This should mimic pcm control signal & open reg. I should see vacuum at the gauge. Correct?
 

billr

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#11
Another useful test would be to disconnect the electrical harness from the solenoid valve, then connect a low-wattage 12V lamp to the harness in place of the solenoid. Connect the lamp with long leads and drive around a bit to see if the PCM commands that "solenoid" (lamp) on/off periodically. By low-wattage I mean something like an instrument panel lamp, not a head or brake lamp; we don't want to over-load the driver in the PCM! Although I would expect that driver to be internally-protected against both over current and temperature, let's not take a chance... It may be something as simple as crud in the EGR passageways that can be cleaned out. Yes, I think you are interpreting kev's test of the valve correctly.
 
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#12
yes you got the plan......

THe only reason to disconnect and jump 12v and ground to solenoid is an abundance of caution.
As mentioned fingers crossed its just a bad solenoid...
 
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#14
Kev,

I did jump the vac reg & it did send vac to the egr. vac reg itself had 40 ohms resistance. Next step? Check VT wire from pcm pin#47 to reg harness connector? Can I check the wire for resistance with battery disconnected & T pins inserted in wire without unplugging pcm connector?
Billr
I did run a test light setup with a low watt bulb socket. Test Drive did not make the light come on. 35mph, 55mph & acceleration.
 
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#15
you know this - we need to check condition of wire to PCM, is it open?