Tested immo off solution for late 90's Volvos

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Dear members I have something fairly exciting to share.


TLDR;
It's said on forums that there is no immo off solution for Volvo M4.4 (Bosch Motronic 4.4) ECUs. This is so wrong. Because all M4.4 boxes are the same in terms of hardware, and some M4.4 boxes were released without immobiliser functions (the 2.3T for example), it is possible to take the file of the 2.3T ECU, map it, set constants (mainly injector constants) and delete turbo-related DTCs correctly so that it will run your naturally aspirated engine perfectly without any immobiliser required or MIL light. You have to do a minute bit of wiring and make a bridge between 2 lines after you remove the immobiliser to keep your OBD2 port working.




A 1999 Volvo S70 2.5 arrived in the workshop with a faulty immobiliser unit. I looked online but was told in many places that an immo off solution for this car or any of the late 90's Volvos with the Bosch immo box is impossible. However in one place I noticed that Volvo 2.3T engine with the same M4.4 ECU were never fitted with immobilisers.


Anyway, I found a thread and wikia page filled with all sorts of wonderful information on tuning the T5 Volvo engines and provided original files for these computers.


The diagnostic K-line had to be bridged as once the immobox is removed the communication line is broken and diagnostics are impossible. I'll add a wiring diagram soon.


Lo-and-behold after flashing the ECU with a file for a 2.3T the car didn't start.


After a broken camshaft sensor was repaired the car started and ran but very rough and battled to idle.


I wrote the correct injector constants for the vehicle and disabled the turbo related DTCs into the new file and flashed it to the box.
After this the difference was night and day; the car started easily and ran well and didn't show the MIL light.


I tried to ask the customer if he wanted me to play with the ignition timing to try and get it back where it was supposed to be (turbo cars retard timing big time) but he wasn't interested and said he was more than happy with how it was running and just wanted to take the car because it's been to so many "mechanics" before it arrived at us (who I suspect were the cause of the damage to the immobiliser system) that he's just happy the car is driving.


When I explained to the customer that we suspect the original problem with the vehicle was just a faulty camshaft sensor and that the clever mechanics that he sent it to thought it was an immo problem and butchered the immo box to the point of no repair. Tracks broken, pads lifted all over the place, blank data in the eeprom etc etc... The customer was less than impressed with the previous mechanic to say the least (a few swear words were used).


So, by downloading the free TunerPro RT and with a very small bit of reading and learning and assuming you have a basic soldering kit and a programmer capable of writing a 28f010 or a VCDS cable, an immo-off solution for this car is most certainly possible (despite what the naysayers say) and fairly easy actually.


I have attached the file I used to immo off the S70 2.5 with a 0261204295 ECU. I assume it will work for all M4.4 2.5 Volvos.

[Stelaras26]

Very nice job,helped me a lot mate!

Really awesome!

[ray-ray]

That what we need positive solution with detail instructions.. (welcome to the forum) I’m here if you need my help.

[Odemaster]

Hi! Is the wiring diagram still available can't find it from the downloaded files?

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Hi! Is the wiring diagram still available can't find it from the downloaded files?

Hi, apologies. Never got around to uploading it. Fairly simple though from what I can remember; the K-line runs from the ECU through the immo-box to the OBD port's pin 7. After the immo-box is removed you can place a jumper in its connector across both ends of the K-line to test before cutting and joining.