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Main Auto Diagnostic Tool

Main Auto Diagnostic Tool 1

Without keyword

or how to spend three hours diagnosing an elementary problem

Recently, the owner of the Volvo S60 2005 onwards turned to us. with 2.5T engine (B5254T2).
The complaint is: “… writes an error on the dashboard, barely keeps idle, does not respond to the gas pedal”.
That is, there is some kind of emergency mode. The case itself is simple, and this article is not a description of the diagnostic algorithm, but rather, information gathered on this issue together.
However, for those who are just starting to work in this area, the search algorithm itself may be of interest on the simplest example.
So, we started, naturally, with the main diagnostic action – thoughtfully frowned eyebrows, looking at the described behavior. Then we went along a simple path: we connected ELM327 and read errors using the standard OBD-2 protocol. No errors were read, but there was a Freeze Frame – a “cast” of parameters that the engine was working with at the time the error occurred. There he is:

It can be seen that error P2111 was generated. By and large, more Freeze Frame did not give us information. It, however, is not necessary – in the twenty-first century primary information can always be obtained from search engines.
The request “P2111 volvo” issued that it was an error on a throttle valve, but did not give more detailed information – all links led to forums of car owners. These forums are good because they are actually rich statistics: all the characteristic “sores” of the brand on the club forum almost always “splash” somewhere at the top of all topics. The minus of club forums is that people there, although they are extremely interested in fixing the problem, most often specialize in completely different areas, and each such topic on the problem contains only a description of the problem (often inaccurate) and a recommendation like “well, you need this service” . This recommendation didn’t suit us very much, so we decided to go further.
The first thing they did was try to erase the error. Something was erased, and the car even started up regularly – but after some time the problem returned again. And after re-erasing the error, it reappeared, already immediately when the ignition was turned on again.
The situation was confusing primarily by the fact that from the available information (error code + relevant descriptions on the forums) it was not clear – is the problem in the damper itself, or in the gas pedal position sensor? On this car, the throttle is already fully electronic, that is, the control unit receives the pedal position from the sensor, and in accordance with this, it opens the damper at an appropriate angle, controlling its electric motor.
Historical reference
Initially, electronic throttle control was invented by manufacturers in order to fit into environmental standards that were once again tightened. With the direct mechanical connection of the pedal with the damper, in some modes, a sharp opening of the pedaled to unfavorable operating conditions, in which the number of harmful emissions increased. When the throttle opens electronically, the control unit simply will not let it open so that the engine goes into this environmentally unfavorable mode.
So, we have established – the issue is clearly related to the throttle or gas pedal position sensor. In both cases, in a number of situations, the control unit can go into emergency mode, stopping “moving” the shutter.
Fortunately, we still have the next echelon of diagnostics – to take Autocom-CDP +. In our case, it makes it possible to read the errors of the engine control unit not only according to the standard OBD2, but also according to the manufacturer’s proprietary protocol.
And here this opportunity helped‚ we read the error 925C.
And again, “thanks to the search engines!” Who prompted for “volvo 925C” to decrypt “Electronic Throttle Body: signal too high” and a link to several specialized resources that describe both typical errors of these chokes and the experience of other mechanics. This immediately discarded the version with the gas pedal position sensor, saving 15-30 minutes on checking the pedal (remove it, then find the pinout, then check the sensor readings in different positions).
It became clear that the question was a damper. She, as it turned out, Volvo of such years has a rather problematic unit that has the following problems:
– Deterioration of brushes of the electric motor (damper drive).
– The ingress of oil from the inlet to the inside of the shutter (this is a turbo engine, so it is capable of driving oil into the inlet, in principle, ‚is capable of.
– Depreciation.
– Jamming of the damper shaft due to dirt in the intake.
– Deterioration of gears of a damper drive.
– Bad contact on the harness connector.

It is almost impossible to establish a specific reason without removing the damper. Unless the sixth point is solved simply by removing the connector and visual inspection. In our case, the connector was not to blame, although at least one case was detected when the ground contact was poorly tightened – this led to incorrect figures of the current consumption and the damper position received by the control unit, which caused it to generate an error and turned off the damper power.
Well, nowhere to go – I had to shoot. The damper located on this engine is not very convenient, the intake ducts are partially dismantled below in the photos:

Main Auto Diagnostic Tool 2

Now, when it is in our hands, you can go consistently for all the assumptions. So:
There is dirt inside the damper. Not to say that there is a lot of it, and it is unlikely that it can cause the axis to jam:

However, washing is not a long thing:

Considering the symptomatology already described, it is not difficult to check the assumption, just connect the damper to the connector, erase the error, turn the ignition off and on. At the same time and visually check how it all works. It turns out that the control unit slightly “pulls” the shutter when it is turned on, and immediately generates an error.
Well, let’s continue to rule out the reasons. To do this, remove the plastic cover (it rests on the brackets, which are easily pulled off with a screwdriver). Immediately discard the potential ingress of oil into the damper – everything is pretty clean. We also look at the tracks of the throttle position sensor ‚it is clear that the tracks are also an integer. So the wear of the position sensor also sweep.

But the gear has already worn out:

Well, this is a verdict. If for some cars of the VAG group you can still find the shutter gears as a separate spare part (someone very well felt the market niche), then Volvo, apparently, is not such a popular brand.
In fact, in a good way, the error 925C refers more to the excess of the starting current of the damper electric motor and is much more likely associated with the wear of the motor brushes. But in the light of problems with the gear, it’s still pointless to repair only the motor, since problems will soon appear due to the gears, and anyway the need to replace the damper assembly will come.
Afflicting the owner with the need to replace the assembly, we provide the last service – consulting. On the flap, both the original number and the number from BOSCH (which produced this flap) are clearly visible. These numbers are:
VOLVO 30711553
BOSCH 0280750103
A short search showed:
– large suppliers of spare parts offer analogs in retail at a cost of about 9,000 rubles;
– order from China is possible for an analog worth around 5000 rubles.
We did not have information about the reliability of this or that option, so today’s diagnostics was completed and the owner was sent home, pondering, negotiating with his budget, and so on..
Based on the results of this diagnostics, it remains for us to understand that the main resource in our time is knowledge. For all the described time, in essence, only a diagnostic scanner was used – to read and erase errors, and the time of “net” use was a maximum of 20 minutes. Everything else – search engines, meditations and general knowledge about the device of the car and injection control systems. From which we once again conclude that information is the main diagnostic tool that must be constantly updated with all available methods.
If we had a little more information at the beginning of the repair, everything would come down too quickly dropping off the damper and “sentencing”. We hope that today’s material will be worthy replenishment of the piggy bank with this very information.


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