Car Mitsubishi RVR, 2.4 liter, 1999 release, GDI. A good example of a “floating fault”: “the engine may start, or it may not start”.
When the ignition switch was turned on, the CHECK ENGINE light flickered on the instrument panel, but did not light up at full strength. In addition, as the car owner said: “Under the hood, something rattles”.
In such situations, the first question is: “Where and where to start troubleshooting?”. My search was built this way (in this case):
1. There are no direct hints in the form of available trouble codes – this is to the side, we turn our attention to another
2. Are there any indirect clues? There is. This is the “rattle of something under the hood” and the “flickering CHECK lamp” on the dashboard.
Next, you need to try to determine “what rattles there.” As it turned out, this is a fuel pump relay.
Why did the verification begin in this order: “Due to the fact that there was a periodic flickering of the“ check engine ”lamp and the relay was sized, the search for the problem began by checking the supply voltage of the components related to the injection and ignition systems. In this case, these are fuses and relays (fuel pump relay, etc.) ignition coils.
Next, you need to open the circuit and see “what circuits are tied to this relay and around?”. We look:
At first glance, nothing interesting? Well, why … let’s check the relay itself, a hint for checking is in the Motordat program itself:
Checked. Conclusion: “the relay is operational, the reason for its rattling is in something else.” We look further at the same time according to the scheme, and “on the ground”:
Light bulb CHECK ENGINE on the diagram:
If it “flickers,” then maybe “not enough power?”. Let’s check the assumption: for this we measure the supply voltage before and after the bulb. Conclusions: On the 10A fuse (bottom – left on the screen) the voltage is normal. And if you go further along the circuit, then on the ignition coils the voltage is below normal or absent (right on the screen).
Here’s what the voltage test on the ignition coils looks like:
What conclusion can be made? In my opinion, logically true is:
“Since the preliminary voltage measurement, on the fuse” F306 “10A (see Motordata), gave a positive result, respectively, the voltage to the ignition coils is lost somewhere in the intermediate connections or wiring”.
The next step is to check the connectors. And near the connector “B28” (see below the screen of the Motordat program):
A little closer for a better understanding:
Handicraft remaining from alarm installers was detected.
And here is the general troubleshooting scheme and the elements to be checked:
Now we need to mention the history of this repair.
Car owners are manlike and savvy. They themselves diagnosed the malfunction: “Does the lamp blink? Does the relay rattle? This is definitely” BRAINS! ” And they removed the control unit, and went to disassemble, and bought a new control unit. Set – does not work.
As it turned out, instead of the engine control unit, they removed the gearbox control unit. After conducting field experiments on his car, the car owners had to admit that “everything is very bewitched here!” and decide to go to a car service. But even if they removed and replaced the engine control unit, the result was exactly the same, because the cause of the malfunction was different: “The human factor”.
Restoring the logic of the nameless alarm installers, I saw that they took the plus from the ignition on this B28 connector, tore it up and inserted their lock there. Subsequently, other experts removed this alarm, and the wires “just twisted”. And here, large currents pass, hence the bounce of contacts, and the “flickering of the CHECK lamp on the dashboard”.
So, if there are no obvious hints in the form of fault codes, then the fault can also be calculated by indirect signs.
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