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Yesterday, out of nowhere, my Maxima would not rev pass 2700 RPM. This happened during highway cruising too. So, I pulled over and ran the scanner and I got P0403 (EGR Circuit Malfunction) and P0505 (IACV). I cleared it and and the P0403 came back right away while the P0505 went away.
If the car wasn't moving, I could rev the car all the way just fine, only during driving mode. I decided to remove the EGR tube (again) and see if they were clogged after cleaning it a week ago. It looked brand new. Took throttle out and removed the IACV and looked cleaned. Finally took the EGR valve and the solenoid out too. All passages looked cleaned.
Below is the summary of what I did. You guys should follow the FSM, which I did, to do this to avoid any more headache.
1. CHECK EGR VOLUME CONTROL VALVE POWER SUPPLY CIRCUIT. This is basically checking the voltage between pin 2 and 5 to ground (use body ground) to see if you get 12 V running thru there. No Problem found
2. I did the test #1 on IACV harness also. No Problem.
3. Checked the Resistant on the EGR Selenoid. This is basically between pin 2 and 1, 3. Also between pin 4 and 5, 6. It should read about 23 ohm. No problem found.
4. I did the same thing for IACV selenoid. It should read about 22 ohm. No problem found.
5. Since the EGR selenoid passed test # 3, I should be able to see the plunger moves when powered thru ECM. I plugged in the EGR harness from ECM to the EGR valve and turned the ignition key on (do not crank it). The plunger didn't move. Took the plunger out exposing the shaft and retested, same thing. So I was like
6. Did the same thing with IACV and the shaft moved, so IACV is all good.
7. For the heck of it, I plugged in the IACV harness to the EGR selenoid (they are identical and have the same principle) and EGR selenoid was functioning perfectly. The shaft moved out then few second later moved back in when the ignition key was off.
So by now I know that the EGR Selenoid is good. I started having butterfly in my stomach thinking maybe my harness is messed up.
I went ahead doing continuity test between the ECM main terminal connectors to the specific F4, F71 EGR connector. I had to create about 10 feet of wire jumper to be able to do it on every pin (1,4,3,6) on the EGR connector to pin (9,10,18,19). FSM showed it in detail. All pins had good continuity except pin 1 to pin 9, it was dead silent. So, I though maybe the connector itself, checked the connector itself and it was good.
So the problem seemed to be a short open condition on the ECM harness at pin 9 which is one of the signals to the EGR Valve stepper motor. I guess basically there is no feedback between the EGR Valve selenoid and ECM and that caused the selenoid to not functioning and ECM went to limp engine mode.
I'm not sure what to do now. Before I start pulling the harness out of there and fixing it, any of you guys have better suggestion. I even tempted to run new same wire instead of taking the dashboard apart to fix a wire. I don't have a bi-directional scanner that can talk to individual sub system and do the closed loop test, but from what I've seen it looked like I have wire harness issue.
This car has been in and out of the garage for various different reasons, but electrical issues are my worst enemy. I was about to rebuild the tranny (input bearings) till I have this issue, the car idles and drives fine except it won't go pass 60 Mph.
So the problem seemed to be a short open condition on the ECM harness at pin 9 which is one of the signals to the EGR Valve stepper motor. I guess basically there is no feedback between the EGR Valve selenoid and ECM and that caused the selenoid to not functioning and ECM went to limp engine mode.
"Short open" does not make sense, but I assume you wanted to say "open" - that makes sense.
Harnesses usually don't brake in the middle, so let's assume the ECU-EGR connection is broken at one (or both) ends - i.e., at the EGR connector and/or the ECU connector. If a detailed inspection does not reveal a problem, I would install that "temporary wire" fix you mentioned earlier and see if it indeed works; if not, the problem must be something else.
Also, I would repeat your connectivity test and make sure that the ECU-EGR line is indeed open.
"Short open" does not make sense, but I assume you wanted to say "open" - that makes sense.
Harnesses usually don't brake in the middle, so let's assume the ECU-EGR connection is broken at one (or both) ends - i.e., at the EGR connector and/or the ECU connector. If a detailed inspection does not reveal a problem, I would install that "temporary wire" fix you mentioned earlier and see if it indeed works; if not, the problem must be something else.
Also, I would repeat your connectivity test and make sure that the ECU-EGR line is indeed open.
I had the same thought that the harness breaking down in the middle is somewhat weird, but it could be something to do when I moved the harness around during my valve cover gasket R&R last time and somehow I damaged it.
I'm going to check that connectivity again tonight on both the ECU side and EGR side. If I can splice that green wire up and chase it with connectivity test again that would at least tell me when the connection is breaking down.
Well, I got the connectivity in all pin now. There was a plug connector (by high pressure power steering line) that loosed its connection. Apperently someone in past before my time fixed something on this juncture and I could wiggle the connector and would loose/gain connectivity between the EGR connector and ECM plug.
Fixed that and all terminals got connectivity now, but the EGR selenoid still didn't move when I put everything back together and turned ignition key on/off.
Here is the video of the test with both IACV and EGR selenoids connected to its connector. You can see that the IACV seleoid worked and the EGR selenoid didn't
Here is the video of the reverse test. I powered in the EGR selenoid using IACV harness and vise versa. The EGR selenoid worked and the IACV selenoid didn't.
So it seems like the EGR harness is still at fault eventhough the circuit is all good now?
I'm stuck and could use some helps.
Your experiments do suggest there is something wrong with the harness connector (F4, F71). It's back by the firewall (see the FSM, pg. EL-356). Also, pins (9,18,10,19) on the ECU connector are also suspect. Verifying the connectivity for the four lines (ECU pin 9 to EGR pin 1, ECU pin 18 to EGR pin 3, etc.) should be a good first step.
Your experiments do suggest there is something wrong with the harness connector (F4, F71). It's back by the firewall (see the FSM, pg. EL-356). Also, pins (9,18,10,19) on the ECU connector are also suspect. Verifying the connectivity for the four lines (ECU pin 9 to EGR pin 1, ECU pin 18 to EGR pin 3, etc.) should be a good first step.
Thanks for the respond.
I did verify that the ECU to EGR pins. At first, the pin 1 on ECU to pin 9 on EGR was dead silent. Later on I found that there was another sub harness connector (by wiper motor assembly) that was dirty and causing that connectivity issue between pin 1 EGR to pin 9 ECM. Fixed that but the EGR solenoid still not functioning when ignition key on. The EGR solenoid resistances are good also per FSM value.
Here are my possible potential root causes:
1. Maybe the harness has too much resistant enough to effect the current delivery even though the continuity test is good? I guess I'll have to measure the voltage drop on EGR connector pin 1,3, 4, 6 and see if they are low.
2. Shorted somewhere. I guess test # 1 above should tell something about this too.
3. Fried ECM causing to loose those 4 signals.
Here are my possible potential root causes:
1. Maybe the harness has too much resistant enough to effect the current delivery even though the continuity test is good? I guess I'll have to measure the voltage drop on EGR connector pin 1,3, 4, 6 and see if they are low.
Too much resistance is a possibility and most likely would be caused by corroded pins in a connector.
But what did you use to measure continuity? If you used an ohmmeter, you would have gotten a high reading. A reading of more than 2 or 3 ohms would be higher than usual for a continuity reading. But I doubt if 5 ohms would be a problem.
Originally Posted by Genes1s
2. Shorted somewhere. I guess test # 1 above should tell something about this too.
Not necessarily. To check for a short, you have to disconnect both ends of the wire and check for continuity between the end of the wire and chassis ground.
If you did have a short, you would most likely be blowing fuses.
Originally Posted by Genes1s
3. Fried ECM causing to loose those 4 signals.
A possibility. You would have to try another known good ECM or sent your ECM to one of the many repair places and see what they say.
OK, phew...I think I may have solved the issue here but lets wait for few more miles. It's been about 50 miles since the fix and the P0403 hasn't returned. I did have P0505 but I think its because my idle is 850-900 after all the cleaning of the TB, IACV, EGR ports, EGR valve.
So here is the summary.
I did all the test on the FSM and they all passed except the last test when it says I need to hook up the EGR selenoid to the harness and see if the shaft moves or the plunger opens and closes. So I hooked it up and the shaft didn't move and I thought I have bad EGR valve. So, I used another known good EGR and tested it with my car and it failed the same way as mine did. I measured the feedback signal on all the 4 pins of my EGR and compared it to the other and they were all identical.
So this was what puzzled me, the FSM test on this indicated that I should have bad EGR valve but a known good EGR valve failed this test too.
So I decided to put everything back together (using the original EGR valve from my car), thoroughly cleaned everything, and put new gaskets (again). The car has been running well so far. We'll see if the code comes back.
So far, the root cause of this issue was the bad connection on the engine harness. There was one big green connector by the wiper motor that when I wiggled the pin wire #9 on that connector , I would lose connectivity between EGR pin #1 and ECM pin #9. That intermittent connection condition could happen when the harness moves around when the engine revs up/down and caused the ECM to not have proper feedback from the EGR system.
So moral of the story, If you have this P0403, CHECK your wiring harness BEFORE you took the system apart which I did. It would have been a 5 minutes job to do this to back probe the EGR connector, ECM, and everything in between with multimeter.
Without reading absolutely everything so pardon me if it's been covered... But I learned about a weak spot in the engine bay ecu harness. All the codes you threw are linked to this section of harness. This information was actually kind of hard for me to find but my 2k1 Gle threw an open circuit code for the tps shortly after I removed the swirl valve butterflies and port and polished my lower intake. Turns out that when I was in the teardown process after disconnecting the coil packs, fuel injectors, iacv, tps, bank 1 (rear) 02 sensor, and whatever else I can't remember... I threw harness and connectors over my passenger side fender seeing as gathered in it's entirety shortly before the firewall after a couple curves. Well in and around those curves the wires are apparently not treated well by the heat due to poor insulation and covering in sections. Makes the actual wires insulation around the copper hard and brittle. Dry rotted so to speak. Sometimes apparently moving them will break some of them. Sometimes not touching them at all doesn't mean they won't break. It was actually causing my transmission that before all the work I did never slipped to slip in certain gears at certain times. When I finally found what the problem might be and track down the open circuit... It was in the midst of those curves nowhere near a connector, terminal, or splice... It's the ecm harness engine bay or something like that.
Well it's been 100 miles now and the P0403 hasn't come back yet. The P0505 is also not coming back so looks like its all good perhaps.
I learned that FSM troubleshooting for the EGR is not accurate, so be careful following the procedure.
Understanding what the solenoid does and how it interacts with the ECM was the key for me.
Now I can tackle the tranny rebuild process next..
I hate to get the 2k1 gle running because I totaled my truck due to someone being in too big of a hurry to yield. The 5 speed is still awaiting tranny rebuild and other love. After a crap ton of money, pen parts, my time, my labor, some preventative maintenance along the way she fired up, took idle relearn, still slips, no codes, bucks in first, and hesitates in neutral if throttle is barely pressed. Popular vote is the maf which is the only unchanged part so makes sense especially considering mafs don't always throw codes, datascan 2 shows it working ok, and it's over $100 at rock auto. Waiting for it as we speak. In the mean time found a short in tps 5v wire and proceeded to investigate. Worked my way back to the ecm harness connector and when I removed the connector could have screamed... motor oil all over connector and ecm where it snaps in. At some point in this cars life oil from the rear valve cover I'm guessing because that gasket was kinda fresh leaked onto the ecu harness and ran it's course all the way to the ecm... I cleaned it with crc, put a healthy coating of dielectric grade on and around the connector, plugged it in, greased every other connector under the hood, sprayed the harness off as much as possible but it was raining, and awaiting daylight to go out there and see if it helped or i still have a short. What are the odds right?
So, the P0403 came back after 6 months. The car has been running perfect, idles perfect too, just the P0403. It came out of the sudden and lost power under heavy acceleration pass 2800 RPM and SES light came on few sec later. I've been driving it like this for days now, sometimes I cleared the code, car ran great for a day then the damn thing came back again. I didn't clear the code anymore, just drive under new speed limit of 60 mph
Might have to check the wiring again and see what's up.
So, the P0403 came back after 6 months. The car has been running perfect, idles perfect too, just the P0403. It came out of the sudden and lost power under heavy acceleration pass 2800 RPM and SES light came on few sec later. I've been driving it like this for days now, sometimes I cleared the code, car ran great for a day then the damn thing came back again. I didn't clear the code anymore, just drive under new speed limit of 60 mph
Might have to check the wiring again and see what's up.
350z headlight harness is the EGR plug . I bought one for like $7 on eBay.
I also re-routed the wiring harness from
behind the engine to on top of the engine for easy access Andy away from the heat. I found that the secondary connector to the egr temp sensor was melting too.
So the saga continue. I no longer have P0403, but it is now P0400 which is Exhaust Gas Recirculation Flow Malfunction. Possible root cause and finding.
1. No clogs. Port, tube, and everything else are clean.
2. EGR Valve plunger is clean and doesn't stuck close.
3. Battery is good
5. The EGR Selenoid resistance checked out, other than that solenoid won't power up at ignition ON, but this condition had no affect on the system ( no codes, P0403 was due to harness intermittent connection issue).
6. Signal & power on the harness checked out.
7. EGR temperature sensor and circuit. Need to check.
8. Exhaust gas leaks. Everything is tight, but will double check
I really think this is still electrical intermittent issue....
I will get rid of EGR next year since we don't have emission anymore here in area.
So, finally was able to check the EGR temp sensor. It is in working condition. Exhaust leak is possible but I have to make the running again to check this.
I doubt the EGR valve it self is the issue. The ICV solenoid is similar to the EGR solenoid and the ICV solenoid cycles when the key is ON. So I plugged in the ICV harness to EGR solenoid and it cycled fine. I could see the spring plunger of the EGR valve moved.
So my questions, it does the EGR valve normally get cycled when the key is ON. The FSM mentioned about this test and when the EGR valve isn't cycling when key in ON, it would indicates that the EGR is malfunctioning and need to be replaced. I just checked my EGR selenoid is working OK when I plugged it in to the ICV harness.
this leads me to believe that the ECM didn't have the signal ( it has powers and good connectivity) to cycle the EGR when it is needed, but the code is P0400 not P0403...
How do you check for this signal? EGR is only open at certain engine load , temp, and RPM. I don't have Consult or anything that can cycle/monitor signal from the ECM.
So, the P0403 was off for about 500 miles then it decided to show up again for the last couple months.I didn't bother to trouble shoot it because Covid was slowing the need to drive but now that I actually need to get places more often, its annoying to drive with 2800 rpm limiter.
I've pretty much exhausted every diagnosis that I can think off (https://www.scannerdanner.com/forum/...m.html?start=0) and the car runs perfect other than 2800 rpm limiter (limp mode). The limp mode is gone if you shut the car down for 20 minutes and it always comes back on after 15 miles of driving every time.
Its either ECM or Harness issue. I'm 95% confidence it is not the harness issue. The safest way would be getting the original ECM looked at and pull the hardness out for inspection which I might still do but wondering if going with 2001 ECM would solve my issue and get rid of my EGR all together. Would the 2001 ECM plug and play?
05-30-2018, 09:40 PM
