v70 2.4D Euro4 06 163bhp DTC P0489 (P0403 now cleared)

[FlyNavy]

Hi,

Code definitions
P0489 - EGR A Control Circuit Low
P0403 - EGR A Control Circuit/Open

Here is what has happened...
First really cold morning I went to drive car and instantly there was no power, just a slow linear rev increase with no boost. It can drive up to any speed but hills require down gearing and fuel ecomony realitively normal. Engine Service Required Light on dashboard.
By the time I was coming home from town the power came back again and car was normal but light was still on. For 2 days the light was on but car had power and on 3rd day light went out. Then next overly cold morning the light came on and the power was gone again. This has not changed since. Pity as I need to tow a trailer and this ain't happening right now.

I went to local repair shop to check codes and he just said about EGR needing investigated and code comes back as soon as it is cleared and so I went home thinking of the mounting list of things wrong with this car needing repaired!!!!!.
Having recently seen something online about the crud that gathers in the EGR and associated pipes up into the inlet manifold I thought first thing I will do is clean that out and sure enough the EGR and pipe to the left that attaches to top of manifold was full of crud. I did not remove the EGR to do this, took out air box to the right and the pipe to the left then just scraped out the inside of the EGR and the removed pipe, and washed out with carb cleaner. The pin in the middle of the EGR was well cleared of crud especially around both ends of pin, as clean as one could make it.
Put it all back together and problem still was there. Was it because the codes not cleared, so I bought a reader to clear myself rather than go to garage again.
On first reading I got 2 codes as above, I cleared them and instantly one code came back the other has not returned. The code coming back was the P0489.

Would the above suggest that due to crud the pin/something remained open perhaps causing P0403 and due to stickiness the 'EGR Valve Stepper Motor' has failed giving P0489, I've cleaned inside the EGR, the pin is no longer open and the EGR Valve Stepper Motor is tits up?
I read that here https://www.partsforvolvosonline.com...oducts_id=8461

If I was to replace this then I suppose it woud fail again if the EGR pin was having issues despite my cleaning of it, so rather than buy a new stepper motor getting a second hand egr with stepper motor on it is best and cheaper than a new stepper motor?
I can only assume the collant part of the EGR does not need replaced and has no bearing on this error. I will also say that the Throttle Flap to the right of the EGR was taken off and cleaned and the flap can be manually moved and flips back when finger is removed.

These I am not sure about, is this easy, is this likely to be also a problem associated above and the above it fine its these that could be the reason?
- Test EGR control solenoid connector for a voltage and ground signal
- Test for a voltage signal between the ECM and EGR electrical connector

I don't think its about vacuum pressure and valve opening as the core problem seems to be the Control Circuit Low, flagged as soon as the ingnition is on.

Current existing issues, swirl flap plastic end is broken off so (the missing!) bar connecting to actuator cannot be refitted and have checked the Turbo Control Valve and not getting vacuum from the pipes going to the engine mounts. These I believe have only minor effects on performance and should have no direct effect on EGR operation.

Unless there are any smart ideas out there for a fix, I assume its an EGR/stepper motor replacement? (but could be the power to the EGR that is the issue?)
Do I really need to check the power to the EGR first before wasting time and money replacing (ebay!) however if it had been that failed surely that would have been failure complete and not come back for a few days before failing again. That is why I a lean towards sticking EGR, stepper motor struggled to actuate, came back, then under pressure from crud stepper gone?