Hi Folks,
241K miles now.
Prior to test:
Replaced cats last month. It was clogged and heating up the floor pretty bad.
Disabled Pair valve which was the cause of my Code 25 and 26. Stuck and corroded valve.
New O2's
New egr temp sensor
Dorman VSV
AC Delco charcoal canister
Morning of test I noticed my E and R ports were clogged again, cleaned.
Thought I was ready so off I went.
Comprehensive visual inspection PASS
Functional check FAIL( EGR no vacuum when revving)
Emmision test PASS (haha emission passed even with disabled PAIR)
After test======
EGR valve:
Engine dies when applying vacuum. Nothing clogged.
Removed valve, applied vacuum with hand pump while plugging opposite end and it holds vacuum.
Bad modulator:
Blew from bottom and heard air going through port R.
Replaced from Autozone for the same exact one, Denso, with a $10 discount - $84 not bad.
EGR temp sensor:
Verified both wires from ECM to harness have continuity.
Getting 4.95V at harness when IGN switched on.
Oil test from FSM..all temp range OK but in the 302 deg F range I was getting around 4.x K ohms.
Just a little above the 2 - 4K ohm range.
Installed a 3.3K Ohm resistor in place of the temp sensor, unplugged ecm harness and measured 3.28K Ohms at the ECM harness side.
Dorman VSV:
Resistance test ok. No short to body from terminals. Voltage applied and it clicks.
When voltage applied no air can pass.
I don't use the intake manifold pipe.
Bypassed this by routing hose outside of manifold direct to EGR valve as my VSV is zip tied to manifold.
Checked continuity for each of the wires from ECM to VSV harness.
When I direct connect EGR port on ECM to body ground VSV clicks.
Removed throttle body and upper intake chamber.
Clogged metal Y pipe that joins EGR vsv with an adjacent VSV, cleaned.
Clogged EGR passages of intake chamber, cleaned.
Just replaced all rubber hoses.
Ports E, P, and R have no vacuum at idle and have vacuum at 3500 rpm.
Circuits that I could see on the wiring diagram that are connected to EGR temp sensor are VAF, ECT, and TPS sensor via the Br-B wire.
Performed on vehicle resistance test of TPS and all checks out.
My VAF did leave me stranded due to a bent fuel pump switch in it but bent it back and works now. I have a thread on this somewhere.
Later found out that all of the 3 wires inside it were disconnected from the board, since I've had it, but had them soldered properly. Resistance test checks out too.
Per FSM only inputs to EGR is Batt(input 9) and ECT(input 1).
Battery is almost 7 yrs old.
Disconnected ECT harness and get 4.95v when IGN is on.
Measured resistance without removing ECT, both hot and cold and all resistance checks out.
After warming up engine, disconnected the ECM harness for the ECT.
Measured resistance and got .3K ohms. (FSM .2 - .4K ohms 176 degress F.)
Vacuum test:
Ports E and R are clean and have vacuum.
Vacuum from Port Q hose leading to EGR valve is good.
Perfomed the FSM test where you disconnect the hose leading to port R of modulator then connect a different hose to it and connect the other end to intake manifold. I connected it to the brake booster hose.
Since my VSV is not responding I plugged the other side of the EGR with my finger to simulate VSV working and got a really high vacuum when revving to 2500 rpm.
Vacuum test while driving:
T'd between EGR and VSV and routed the hose through firewall to my gauge.
Idle and WOT no vacuum.
Slight throttle got up to about 4 in/HG.
T'd between modulator and EGR valve, same results.
VSV Voltage test:
Disconnected VSV and ran some jumper wires from VSV harness to my DMM inside the truck.
When revving while parked the most I got was anywhere from .2x to .5x V.
I don't remember if it was the moment I shifted to D or the truck started moving that the voltage started increasing to 13.5x V!!!!!
Since everything checks out it leads me to replace the ECM.
But why will the VSV get proper voltage only when driving?
Only difference I could think of is it could be the VAF as the difference between being parked and driving is air flow, considering only possible circuits that are connected to the EGR.
Getting tired and impatient so bit the bullet and ordered a used ECM on ebay.
If it doesn't work I have a backup if nothing is wrong with it.
Appreciate any inputs you have.
Thanks.
241K miles now.
Prior to test:
Replaced cats last month. It was clogged and heating up the floor pretty bad.
Disabled Pair valve which was the cause of my Code 25 and 26. Stuck and corroded valve.
New O2's
New egr temp sensor
Dorman VSV
AC Delco charcoal canister
Morning of test I noticed my E and R ports were clogged again, cleaned.
Thought I was ready so off I went.
Comprehensive visual inspection PASS
Functional check FAIL( EGR no vacuum when revving)
Emmision test PASS (haha emission passed even with disabled PAIR)
After test======
EGR valve:
Engine dies when applying vacuum. Nothing clogged.
Removed valve, applied vacuum with hand pump while plugging opposite end and it holds vacuum.
Bad modulator:
Blew from bottom and heard air going through port R.
Replaced from Autozone for the same exact one, Denso, with a $10 discount - $84 not bad.
EGR temp sensor:
Verified both wires from ECM to harness have continuity.
Getting 4.95V at harness when IGN switched on.
Oil test from FSM..all temp range OK but in the 302 deg F range I was getting around 4.x K ohms.
Just a little above the 2 - 4K ohm range.
Installed a 3.3K Ohm resistor in place of the temp sensor, unplugged ecm harness and measured 3.28K Ohms at the ECM harness side.
Dorman VSV:
Resistance test ok. No short to body from terminals. Voltage applied and it clicks.
When voltage applied no air can pass.
I don't use the intake manifold pipe.
Bypassed this by routing hose outside of manifold direct to EGR valve as my VSV is zip tied to manifold.
Checked continuity for each of the wires from ECM to VSV harness.
When I direct connect EGR port on ECM to body ground VSV clicks.
Removed throttle body and upper intake chamber.
Clogged metal Y pipe that joins EGR vsv with an adjacent VSV, cleaned.
Clogged EGR passages of intake chamber, cleaned.
Just replaced all rubber hoses.
Ports E, P, and R have no vacuum at idle and have vacuum at 3500 rpm.
Circuits that I could see on the wiring diagram that are connected to EGR temp sensor are VAF, ECT, and TPS sensor via the Br-B wire.
Performed on vehicle resistance test of TPS and all checks out.
My VAF did leave me stranded due to a bent fuel pump switch in it but bent it back and works now. I have a thread on this somewhere.
Later found out that all of the 3 wires inside it were disconnected from the board, since I've had it, but had them soldered properly. Resistance test checks out too.
Per FSM only inputs to EGR is Batt(input 9) and ECT(input 1).
Battery is almost 7 yrs old.
Disconnected ECT harness and get 4.95v when IGN is on.
Measured resistance without removing ECT, both hot and cold and all resistance checks out.
After warming up engine, disconnected the ECM harness for the ECT.
Measured resistance and got .3K ohms. (FSM .2 - .4K ohms 176 degress F.)
Vacuum test:
Ports E and R are clean and have vacuum.
Vacuum from Port Q hose leading to EGR valve is good.
Perfomed the FSM test where you disconnect the hose leading to port R of modulator then connect a different hose to it and connect the other end to intake manifold. I connected it to the brake booster hose.
Since my VSV is not responding I plugged the other side of the EGR with my finger to simulate VSV working and got a really high vacuum when revving to 2500 rpm.
Vacuum test while driving:
T'd between EGR and VSV and routed the hose through firewall to my gauge.
Idle and WOT no vacuum.
Slight throttle got up to about 4 in/HG.
T'd between modulator and EGR valve, same results.
VSV Voltage test:
Disconnected VSV and ran some jumper wires from VSV harness to my DMM inside the truck.
When revving while parked the most I got was anywhere from .2x to .5x V.
I don't remember if it was the moment I shifted to D or the truck started moving that the voltage started increasing to 13.5x V!!!!!
Since everything checks out it leads me to replace the ECM.
But why will the VSV get proper voltage only when driving?
Only difference I could think of is it could be the VAF as the difference between being parked and driving is air flow, considering only possible circuits that are connected to the EGR.
Getting tired and impatient so bit the bullet and ordered a used ECM on ebay.
If it doesn't work I have a backup if nothing is wrong with it.
Appreciate any inputs you have.
Thanks.