There are certainly many other faults in the environment of modern direct injection engines. There will always be faults, the cause of which will not be immediately obvious (and most of all, reading the fault memory and self-diagnosis will not always help!). Therefore, one should master the skill of systematic system analysis, as well as the fault finding technique.
Always read the fault memory first. The failover program is usually activated depending on the controller's decision about the severity of the fault, to avoid damage to the engine. This is usually done by reducing the size of the injected fuel doses. Their size can be determined in mg / stroke by measurements during the required rotational speed (guide value for a 4-cylinder engine – 32-42 mg / stroke at 4000 rpm). Without a diagnoscope, you can use an opacimeter and, based on the course of smoke during free acceleration, make an accurate assessment. The condition is appropriate experience.
Experience is also needed for the correct interpretation of the self-diagnosis fault memory contents. Engine temperature slightly too high, e.g. due to partial clogging of the radiator or stuck thermostat, may indirectly lead to a drop in power, because the controller reduces the amount of injected fuel doses or activates the emergency operation program also then, when the fault is not directly related to the electronic engine control (EDC)!
The faulty component can often be identified immediately on the basis of symptoms reported by the customer or found during a test drive. The table below and the faults read in the fault memory should help you choose the right strategy for subsequent component checks.. Using single measurements, you can clearly locate the damaged part and save the customer having to replace entire assemblies. The order of the components in the table is random and has no relation to the probability of detecting a fault.
Fault finding table
| Component | Saving the fault in the fault memory | difficulty starting | Reporteddecrease
power |
symptomsjerks | impossibleliveliness
launched property |
the remaining |
| Injector | lack | x | x | x | – | |
| Spray needle lift sensor | possible | x | x | -1) | hard work (rattling) at low engine speeds. uneven engine operation | |
| Boost pressure sensor | possible | – | x | probableSimilarly | – | |
| Intake manifold pressure sensor | possible2 | – | x | – | – | black smoke when fully loaded |
| Flow meterair | possible2 | – | x | probableSimilarly | – | "Soft" jerks under load, black smoke |
| catalyst | lack | – | x | x | – | |
| Turbosprężarka VTG | so2 | – | x | – | probableSimilarly | to check, whether the power has not been increased, this is often the cause of the damage |
| EGR valve | possible | x3 | x | – | _3 | black smoke when fully loaded, increased fuel consumption |
| Pedal position sensoracceleration | so | x | x | probable-Similarly4 | increased idle speed (the controller works in emergency operation mode | |
| Brake light switch | so | x | the same effect as if both brake light bulbs blown out at the same time | |||
| Injection pump | possible | x | x | x | x | 6 |
| Voltage supply relay | possible | x | x | x | probableSimilarly | often the fault is only temporary |
| ZZ position sensor | so | x | x | – | probableSimilarly5 | it does not measure rotational speed |
| Power system | lack | x | x | x | x |
1 In case of simultaneous damage to the position sensor ZZ, the motor stops.
2 “Boost pressure control differential or intake manifold pressure too high / too low”. Most often, without a clear indication of the component. Further fault finding necessary.
3 Blocked EGR valve (e.g. osadami nagaru, mechanical damage).
4 The engine is running in emergency mode, the vehicle can still be driven.
5 If the sprayer needle lift sensor fails at the same time, the motor stops.
6 Preliminary checks: timing phases, start of pressing (at least statically, better dynamically), compression in cylinders, ESP electric cables (possible damage), fuel supply system, voltage supply (relay), the size of the injected fuel doses (from the measured values, chip tuning).