I'm consistently getting code 5 (Exhaust gas recirculation faulty) on my 1995 E320 with 170k miles. I've read thru the archives and and 98% confident EGR working properly. I've checked the following:

- Applying vacuum to the EGR valve at idle cause the engine to stumble; I also replaced the EGR tube at 150k miles when replacing the head gasket

- EGR valve audibly snaps shut when vacuum is removed; it also has the white dot so I assume it has been replaced by the previous owner as a result of the TSB

- Applying 12v to the SOV also causes the engine to stumble at idle

- Air Pump and EGR valves are not reversed

- While driving, I monitored both the vaccum at the EGR valve and voltage to the SOV. EGR is activated with the engine warm around 1500 RPM and cuts out at idle and deceleration

- Wiring Harness has been replaced and is in good shape

The car runs fine. There are no codes on pin 8 or 14. Code 23 [Intake manifold pressure (in base module pressure sensor-) with engine running too
high/low] along with code 5 does appear on the builtin DM before the check engine light comes on; however, by the time the check engine light comes on code 23 is gone. Does this mean the EGR valve could be leaking?

What else can I look for? How does the HFM controller "know" that the EGR is not working? Thanks for any guidance.

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as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5

EGR 5 coupled with 23 is telling you that you may have a low vac condition or the pressure sensor is going..
I would first see if the EGR HOLDS vac with a hand pump.
Then I would take an intake vac reading @ idle.
EGR monitor is the PS and a low intane vac supply may not be enough to activate the EGR when called for ..It takes > 13 "

Also, [ long shot] , you will notice that the SOV has a litttle vent..that could be plugged..when they get plugged , they do not allow venting of the valve when they close, so that traps the vac in the line from SOV to EGR at close, making the EGR remain slightly open...remote possible.

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A Dalton

Thanks Arthur.

EGR valve does hold vacuum when pumped down; engine vac @ idle is 20" (as read from the hose that feeds to SOV). Is that high enough?

I'm pretty sure the vent on the SOV is okay because I pull vac before the SOV and activate by applying 12v, the EGR valve clicks shut when removing the 12v.

Where is the pressure sensor?

as ever
Paul

Look on the driver side /inner fender ..little 1" square sensor with a white/plastic vac hose going back to the intake..that reports intake p/vac back to the Control unit..
Check that plastic line....they crack from heat fatique...I just junk them for a full length rubber vac line. Check the elbow at the intake end of that line too..they split.

If you have the CD or schematic , it is sensor B5/2...

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A Dalton

Found the pressure/vac sensor easily in engine compartment, but was difficult to find in the wiring diagram and EPC.

Replaced the vac line to the pressure sensor for good measure; also pulled the EGR tube from the EGR valve to confirm EGR valve is not leaking exhaust.

Now I am consistently getting code 23 only after a 2 mile drive. I'll take a longer drive in the morning and will expect to get code 5 as well.

as ever
Paul

It will be part of the schematic for N/59 Diagnostics Module circuits..........
It is 5V referenced .

Schematic 07-7.00 DM

B5/2 Sensor- Location Key 9M
Part 011-542-06-17

3 wire , center tap pot..pressure sensed

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A Dalton

http://www.peachparts.com/shopforum/showthread.php?t=204737&highlight=vacuum+sensor+code+23

It looks like the signs are pointing to a bad sensor based on this thread and the one above.

Is there a test for that sensor? A certain voltage or resistance at a certain vacuum?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I pulled the plug from the pressure sensor and it was visibly corroded; cleaned it up.

I also found the test scenario on the WIS. With the engine running, pressure sensor electrically connected, and vacuum line disconnected: connect a voltmeter on pins 1 and 2. Voltage is supposed to be > 3.5v; Apply > 500mbars and voltage is supposed to be < 2v. Mine was in this range after I cleaned up the plug.

No codes or check engine light after a 5 mile drive; will see what happens this week.


as ever
Paul

That would fit the complaint.........


Another testiment to the saying .." 90% of all electrical problems are poor connections"

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A Dalton

That is great info. I am assuming for the test you apply vacuum and not pressure?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

500mBar is a pressure measure b/c it's reference is Absolute Pressure.

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A Dalton