I want to talk about one interesting case.
1JZ-FSE car, direct fuel injection.
Customer complaints – “Check Engine” banner is lit, significant dynamics deterioration, uneven engine operation increased consumption. According to him, this defect appeared after one of the service stations replaced the piston rings. I went to several places for diagnostics, as a result, at one of the stations the electric fuel pump located in the tank was replaced, with another, after diagnostics, the injector control unit was sentenced by the scanner.
Upon arrival to us, the client had a piece of paper with an error code and a diagnosis, which he did not want to verify at his own expense. Although the money for the “diagnosis” was paid, the client decided to pay for another diagnosis, and make sure the diagnosis is correct. An important factor in making this decision was the responsibility for the “diagnosis” – our responsibility. If he made a mistake, the client purchased the part, but this did not solve the problem – the client is paid the cost of the part, which we keep as a “souvenir” and the cost of diagnostics (or a repeated search for a malfunction). Given the cost of the injector control unit (Ingection Driver), even used, in our area – the solution was logical.
Here are photos of the printouts of the diagnostics with which the client arrived.
A scanner error reading confirmed the presence of this current DTC. P1215 EDU circuit malfunction. The engine worked on four cylinders instead of six. There were no control pulses on nozzles of 3 and 4 cylinders. It was decided to investigate the operation of the nozzle amplifier with an oscilloscope..
The injector control unit itself – Ingection Driver:
Checking power circuits, ground and control signals did not reveal anything suspicious.
But with the rest, many questions arose.
A car with such an engine is very rare in our area, the control system is unfamiliar.
I did not find technical documentation or an article describing this system and decided to figure it out myself.
Below I describe the conclusions reached by studying the oscillograms..
The conclusions – COM1, COM2, COM3, IGF, INJ1, ING2, ING3, ING4, ING5, ING6 aroused great interest. .
The question immediately arises – why are there only three COM signals with 6 nozzles?
The dialer confirmed the assumption – each pair of nozzles has a common COM output.
The measurements were carried out on the connectors of the injector control unit.
COM3 -> ING3, ING4.
COM2 -> ING2, ING5.
COM1 -> ING1, ING6.
Oscillogram of an idle pair of cylinders at the time of start and first seconds of engine operation.
Immediately struck by the “drift” of the constant component of the voltage level on the waveform (1.18 in this and 2.94 in the next).
Oscillogram of an inoperative pair of nozzles after 5 seconds of engine operation.
Oscillogram of a normally working pair of cylinders at the time of start and the first seconds of engine operation.
On this and the next waveform, we notice the following:
-dc level stable.
-at the time of start, there is impulse noise at the moments of operation of one of the nozzles of the idle pair (it can be seen from the waveform if you count by the engine’s clock cycles).
Oscillogram of a working pair of cylinders after 10 seconds of engine operation.
As you can see, after about 10 seconds of engine operation, impulse noise disappears.
The purpose of this signal is to control the operation of injectors for the engine control unit. This conclusion was made.
As you can see – pulse interference is also present.
We examine in more detail the signals COM2 and COM3. The waveform of the signal COM2 (common nozzles 2 and 5 cylinders). Properly functioning cylinders.
The level of the DC component is stable, above 4 volts.
Waveform of the COM3 signal (common nozzles of 3 and 4 cylinders). Not working couple.
As you can see – a complete mess.
At this stage, the following conclusions were made:
– The level of the constant component, something like a current for monitoring the health (availability) of the injector circuit (assumption).
– The common circuit of the pair of nozzles (COM) works similarly to the DIS ignition system (one coil per two cylinders).
– A positive high-voltage pulse is present at the time of each of the nozzles of the pair, but only one will work, at the output, which (ING) the control unit will generate a negative pulse (“land on ground”) at a given time.
– IGF signal; injector operation monitoring transmitted to the engine control unit.
The conclusion suggests itself – if the nozzles are connected in pairs and in the event of an emergency shutdown, both will be turned off, although only one can be guilty.
We verify this assumption by recording the waveform and turning off the nozzles one by one.
We get such an interesting picture:
The level of the DC component on the faulty channel (COM3), when the injector No. 3 is turned off, has come into line with the voltage level of the working channel (COM2).
Turning off nozzle No. 4 constant component level did not change.
Was diagnosed – the injector No. 3 is faulty and its replacement will eliminate this malfunction.
The nozzle was ordered and replaced..
Next photo: Nozzle No. 3 removed from the engine and causing this defect (presumably inter-turn circuit in the winding).
It remains only to speculate – who and what exactly did to her when repairing the engine, as the car for repair stopped under its own power.
The article is mainly aimed at beginning diagnosticians..
The material presented does not pretend to be true in the first instance – these are just conclusions and assumptions.
Bochkovsky Alexey Ivanovich
st. Gagarina 57/1 Service Station Diagnostics of electronic injection systems,
ABS, AKPP, repair of electronic components. Repair of immobilizer systems, electronic locks and Mercedes keys
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