I checked the codes on my 1995 Volvo 850 and I got the 2-4-1 code from the A2 Engine socket. According to the bay 13 trouble codes it means "EGR Flow is Too Low" What exactly does this mean, is it something major to be concerned about? Please let me know, Thanks.

 

If you don't know what EGR is, just google "Exhaust Gas Recirculation" to find a good explanation. Following from manual on this DTC:

2-4-1 (EGR Flow Incorrect)
1) EGR temperature sensor signal should change when signal
from ECU is sent to vacuum controller. If signal does not change, ECU
registers a fault and sets code. Possible faults include:
* Break in signal lead.
* No voltage at EGR controller.
* Faulty EGR controller.
* Poor vacuum supply to EGR valve (White vacuum hose).
* Faulty Yellow vacuum hose.
* EGR valve does not open.
2) To check operation of EGR vacuum controller, start and run
engine so it reaches normal operating temperature. Put hand on EGR
controller and increase engine speed several times over 2000 RPM. If
EGR controller produces a ticking sound, go to next step. If EGR
controller is not ticking, go to step 9) and check voltage supply to
EGR controller.
3) Ensure engine is still running. Carefully disconnect White
vacuum hose from EGR controller and check for vacuum. If vacuum is not
present, check White vacuum hose between controller and intake
manifold. If vacuum is present, go to next step and check vacuum from
EGR controller.
4) Turn ignition off. Reconnect White vacuum hose to EGR
controller. Carefully disconnect Yellow vacuum hose from EGR
controller. Connect vacuum gauge to EGR controller. Start engine.
Increase engine speed repeatedly. If gauge pointer moves rapidly,
verifying EGR controller is passing vacuum, go to step 6) and check
EGR valve. If gauge does not move rapidly, go to next step.
5) Turn ignition off. Carefully disconnect Yellow vacuum hose
at both ends. Check Yellow vacuum hose for blockage. If hose is okay,
repeat test using new EGR controller. If hose is blocked, repeat test
using new vacuum hose.
6) To check EGR valve, turn ignition off. Reconnect Yellow
vacuum hose to EGR valve. Connect vacuum pump to Yellow vacuum hose at
EGR controller. Start engine. Increase vacuum to 9 in. Hg. (30 kPa).
Ensure EGR valve retains vacuum (engine will run rough).
7) If engine runs rough when vacuum pump shows vacuum but
vacuum pump loses vacuum, check Yellow vacuum hose for leakage. If
hose is okay, retest using new EGR valve. Clear codes. If engine idles
evenly when vacuum pump shows vacuum and vacuum pump maintains vacuum,
ensure EGR pipe is not blocked. If pipe is not blocked, repeat test
using new EGR valve. Clear codes.
8) If engine idles rough when vacuum pump shows vacuum and
vacuum pump maintains vacuum, fault is intermittent. Check vacuum
controller connector. If connector is okay, check Green/Brown wire
between EGR controller terminal No. 1 and ignition ECU terminal No. 27
for intermittent short to voltage or ground.
9) If EGR controller was not ticking in step 2), check
voltage at EGR controller. Turn ignition on. Disconnect EGR controller
connector. Connect voltmeter between EGR controller connector terminal
No. 2 and ground. See Fig. 8. If voltmeter indicates battery voltage,
go to next step and check signal lead. If no voltage is present, check
for open circuit in Green wire between EGR controller terminal No. 2
and main relay terminal No. 3. Clear codes.
10) To check signal lead, turn ignition on. Disconnect EGR
controller connector. Connect voltmeter between wiring side of EGR
controller terminals No. 1 and 2. See Fig. 8. If battery voltage is
not present, check for open circuit or short to voltage in Green/Brown
wire between EGR controller terminal No. 1 and ignition ECU terminal
No. 27. Clear codes. If battery voltage is present, go to next step.
11) To check EGR controller resistance, turn ignition off.
Disconnect EGR controller connector. Connect an ohmmeter between EGR
controller terminals. See Fig. 8. If ohmmeter shows 75-95 ohms at 68  F
(20  C), check EGR controller connections for oxidation. Clear codes.
If ohmmeter does not show 75-95 ohms at 68  F (20  C), repeat test using new EGR controller. Clear codes.

 

There are two bolts on the driver side of the intake manifold that keep the egr valve in place. There is a gold pipe running into this as well as two small wires coming off it. Un bolt the gold pipe and clean inside it as best you can and take off the egr valve and clean it out. it will most likely be rock solid full of black gunk

 

Everything seems to check out, but I still get 0 volts across connector terminals 1 & 2.
I do get continuity at one of the #27s (there are four), but also at others. No idea where to go from here. Swapping out the ECU isn't much of an option.

 

Here's the link to the full doc: https://www.volvoclub.org.uk/tech/se...s-NonTurbo.pdf
Pretty sure the pins 1 and 2 reference is referring to the EGR controller; not the ECU pins.

Is this keeping you from getting smog cert or causing run issue? Usually any faults w/EGR is the EGR valve itself as it clogs w/carbon deposits.

 

1 & 2 at the EGR, 27 at the ECU.
Smog is the problem. The car is running great. No error codes.
NO is just out of range (524/502max).
Replaced the air intake and the panel cleared and the pinging went away.
Cleaned and checked the EGR, moves smoothly and holds vacuum.
I have power to the EGR controller (GN). It has proper resistance, and if I put 12V to it, it cycles. The signal lead (GN-BN) has continuity to ECU port 27. Every part checks out, it just doesn't DO anything.
Could the temperature sensor be the problem? How do I check that?

The only thing left that I can think of is a bad ECU (side note: the cruise control hasn'tworked since we got it, everything else works fine), but I have no idea how to test that, and finding a replacement is unlikely.

 

Well I don't have my '95 N/A 850 any more so I can't go out and look at it. And it seems the EGR Controller schematic is NOT included in the 850 System Wiring Diagram. My turbo cars don't have EGR (and I don't miss it!).

Be that as it may, we might be able to figure this out. I think there are some typos in above manual. You confused me when you say there are four ecu pin 27s. No, there are two ecus in that box; one is engine control ecu and the other is transmission ecu. For EGR, you're interested in the engine ecu. On it, there are two ecu connectors, an A and a B connector. B27 is for your fuel pump relay control. The 850 System Wiring Diagram doesn't show anything hooked up to A27, but from other sources I see it's 12v pin. My guess is that's what supplying 12v pwr to the EGR control module. Maybe I'm wrong; maybe you can post pictures of the controller and wiring?

You say you're getting 12v to pins 1 and 2 of EGR controller? Thought you said you weren't in prior post?

Are you sure you verified the EGR valve and port in intake manifold is clear? Check Robert's youtube:

 

I get 12V from green to ground, but regardless of what the engine is doing, I get 0V from green to green/brown. It should jump to ±12V when needed.

As for 27, that was my point. There are two ECUs. Each has two connectors. Each connector has a pin 27. The instructions just referenced 27. There is really nothing to distinguish between the ECUs other than their relative position to the OBD-I. Nothing to identify connectors A or B for each.

Thanks to the link, I was able to run the self diagnostic. The EGR Controller works. It cycles properly during the test. It just doesn't do anything when the engine is running: when it's supposed to. Other than that, 1-1-1 on diagnostic ports 1, 2, & 3. 6 & 7 do absolutely nothing. The EGR Controller cycles on port 2.

The EGR is clean and the diaphragm moves freely and holds a vacuum. The supply tube is clear, and the EGR feeds directly behind the throttle body. All clear.

The only problem is the controller not cycling when the engine is running. The circuit is proven good. It simply doesn't activate when it should.

The only other thing I can think of is the EGR temperature sensor. However, I don't know what my readings should be, or if that could even be a factor.

Thank you.

 

The connectors are labeled A and B, albeit it is hard to see (may need a magnifier ); remove ecu and, facing the white connectors, look just above the 7th top row pin counting from center.
https://www.matthewsvolvosite.com/fo...2137&mode=view

I don't know how the temp sensor plays into this, where it is, or how it's wired in to EGR controller and/or ecu. Suffice to say ecu failures are very rare.

Just noticed ecu pin A35 is labeled "EGR temperature sensor".


Found this:

P - EGR FUNCTION TESTING
1995 Volvo 8501989-95 ENGINE PERFORMANCE
Volvo EGR Function Testing
All Models
EGR VALVE

1) Ensure all connections are tight and does not leak, vacuum hoses connected and not kinked. Check EGR function with cold and hot engine at different engine RPM.
2) With coolant temperature at less than 131 F (55 C), EGR valve should be closed at all engine speeds. If EGR valve is open,replace thermostatic vacuum switch.
3) With coolant temperature at greater than 140 F (60 C), EGR valve should only open at partial throttle. If EGR valve remains closed, check thermostatic vacuum switch by disconnecting vacuum hose from EGR valve and blowing air into it. Air should flow freely through thermostatic vacuum switch, if not replace thermostatic vacuum switch.
4) If EGR valve still will not open or will not close after opening, clean or replace EGR valve.

I don't know what vacuum switch they're referring to? Do you have that on your car? Maybe that's what they used on early incarnations of EGR systems?

Think the N/A is Fenix system: note 8/17 is EGR Controller
If you can verify your system is wired like below schematic (w/regard to EGR controller to ecu pins) then I'd say the temperature sensor is the ECT sensor. Is your engine temp gauge working properly? Might want to check real data w/scan tool.
https://www.dropbox.com/s/16ygnk7yp6...aEgr.JPG?raw=1

 

@hwpatterson2k What car do you have? Do you have a 95 turbo 850? If so, this could be an option: 628 ECU Question - Performance Modifications - Volvospeed Forums

 

95 850 SVV 2.4 VJ GFEK
2.4L Non Turbo

Not exactly sure what I did, but the EGR Controller started working when I hard throttle, so it should be working under medium load like it's supposed to.
Unfortunately, on the way to work (hoping to get it smogged at lunch), the Check Engine light came on again.
Haven't pulled the code yet. Hopefully a transient issue that just needs a reset.