OK I finally just unbolted the pcm. Brown wire 0.6 resistance. When first touch it to ground it flashed .03 than stayed on 0. Positive showed 0. Got the same readings on the red and white wires.

 

OK so your 5V reference circuit is good and the other three wires are all good. That leaves the connectors, EGR valve, its plumbing or the VCM. Do you have any freeze frame data to go with that EGR code, that may help us. Also can your scanner view the EGR valve position in live data?


George

 

I have no scanner. I have only a Bluetooth obd dongle that I bought awhile back just to read/clear codes through my phone. Seems like if I clear that P0404 as soon as check engine light comes on, my gas mileage doesn't plummet as much. Which BTW, gas mileage is what I noticed most and led me to cleaning the EGR, buying the dongle etc. Mechanics just wanted to replace EGR but I've read enough on this forum to know that's not always the fix. The app I've been using is Torque Lite. I've seen other settings on there but don't understand how to use them OR they're only available through full paid version.

 

Sorry don't know why that posted twice.

 

Weather is good now. Do you have any more troubleshooting advice?

 

Make sure that all plumbing and the valve are carbon free and that the valve can move smoothly.

Normally you would monitor the position of the EGR valve with a capable scanner and see if the reported position makes sense. Even better, with a bidirectional scanner you would command the valve to change positions and monitor the result. I assume that you do not possess this capability. That said, you could back probe the sensor output to see if it varies during start up and warm up and see if the values make sense.

George

 

Just getting back to this due to weather and other things. I haven't been able to get the Jimmy started since doing the previous tests. It cranks but won't start, just like it was doing before I replaced camshaft position sensor a few months ago. It has also had the intermittent no start for years that is commonly the ignition switch, so I'm hoping that switch just finally gave up completely. I do have the new switch on hand and plan to install tomorrow. But is there any chance unplugging and testing on the vcm could have done something? I'm sure I got the plugs seated well. 😕

 

Yes, it can be the ignition switch. When it cranks but wont start lets find out why:

Test fuel pressure at key on and during cranking
Check spark at the plug ands on both banks.
Test battery voltage during cranking

If that's not it then we move on to fuel injector pulses


George

 

Went ahead and installed the new ignition switch since I had been planning to do it anyway. Still no start. And now I don't even hear the fuel pump priming, while I could hear it before with old switch. Tried the 12v applied directly to fuel pump prime terminal in fuse box and don't hear a sound. I did that with key off, assuming direct 12v is bypassing everything and hitting the fuel pump directly. Guess it's time to forget the EGR code and figure out if fuel pump is bad. Hopefully will return to finish this thread someday.....sigh...

 

If you have a fuel pressure gauge I would check the pressure at the schrader at key on. If it is zero then you should check the power and ground at the fuel pump connector before replacing the pump. I recently helped a guy that replaced his fuel pump more than once and it was the 12v wire from the relay. With other members it has been the frame ground. I can help with that if you want. Yes the fuel pump priming tab is essentially a line tap in the wire from the relay to the pump. Because of that you can measure there for 12v at key on and that tests the entire power circuit except for the last wire run to the pump.


George