evo8.03

anybody have any ideas SOCAL evo 8 wont pass smog due to egr monitor not setting, no faults. car has no mods not tuned. egr was replaced, drive cycle did not work. and seems like no one does a hot smog around here anymore. driving on expired tags.

CDrinkH2O

iTrader: (7)

If the EGR monitor is not setting in the drive cycle, you should see a check engine light (CEL) and pull a P0401. First check your CEL is working - should light up on key on - if not replace the bulb. Next pull the codes with Evoscan or some other reader and let us know what you see.

For the EGR readiness test to complete, there are a few things that must happen together. First the EGR valve must open when commanded by the ECU. This requires a leak free vacuum line between inlet manifold and EGR solenoid, a solenoid that opens when energized, and a leak free vac line from solenoid to EGR valve. I'm going to assume that your new EGR valve's diaphragm is not punctured. This part of the troubleshooting is where most of the problems are found. It is usually mis-connected vac lines, a failed solenoid or broken wiring. Check them and report back.

Once you have checked routing of the vac lines, tested the solenoid and wiring, make sure the EGR valve is actually opening. Use a hand vacuum pump to suck on on the line to the EGR, and listen for the idle to roughen up as exhaust gasses get sucked into the manifold. If the idle doesn't roughen up when you suck on the valve, pull it off the manifold and check the passages in it aren't blocked up with carbon. I've had to clean mine out a couple of times. Next, once you have got the EGR injecting gasses, the MAP sensor on the top of the inlet manifold must register a tiny vacuum drop when the EGR valve opens. Check your MAP sensor is OK. The ECU runs the EGR test once the engine is fully warmed up, so it also requires a working temperature sensor. Check your temp sensor is accurate. The test also depends on an accurate throttle position sensor (TPS) to tell it when you are opening the throttle, and on your crankshaft position sensor (CPS) to read RPM. Check them both.

Here are some details from the FSM:

DTC P0401: EXHAUST GAS RECIRCULATION FLOW INSUFFICIENT DETECTED
.
TECHNICAL DESCRIPTION
• When the EGR vacuum regulator solenoid valve switches from "OFF" to "ON" while the engine is running, EGR gas flows.
• The ECM checks how the EGR gas flow signal changes.
.
DTC SET CONDITIONS
Check Conditions
• At least 20 seconds have passed since the last monitor was complete.
• Engine coolant temperature is higher than 76°C (169°F).
• Engine speed is at between 1,000 and 2,000 r/min.
• Intake air temperature is higher than 0°C (32°F).
• Barometric pressure is higher than 76 kPa (11 psi).
• Vehicle speed is 1.5 km/h (0.9 mph) or more.
• At least 90 seconds have passed since manifold differential pressure sensor output voltage fluctuated 1.5 volts or more.
• The throttle valve is closed.
• Volumetric efficiency is lower than 20 percent.
• While fuel is being shut off.
• The ECM monitors for this condition for 3 cycles of 2 seconds each during the drive cycle.

Judgement Criteria
• The intake manifold pressure fluctuation width is lower than 3.5 kPa (0.50 psi). When the EGR
vacuum regulator solenoid valve is turned ON.
.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
• EGR valve does not open.
• EGR control vacuum is too low.
• EGR vacuum regulator solenoid valve failed.
• Open or shorted EGR vacuum regulator solenoid valve circuit, or loose connector.
• Manifold differential pressure sensor failed.
• ECM failed.