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Nissan Neo Di – Error P 1232

Nissan Neo Di - Error P 1232 1

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Following its ecology-oriented program, NISSAN has developed engines with direct fuel injection into the combustion chamber (like GDI from MMC and D 4 TOYOTA)

With the installation of high-pressure fuel equipment, common problems were supplemented by problems similar to GDI and D 4. The main one is the low quality of gasoline, the chemical purity of which in Russia leaves much to be desired. Unlike diesel engines, where the plungers of high pressure pumps are lubricated (and cooled) by diesel fuel, the plungers of gasoline pumps are not lubricated by the definition of the chemical formula of gasoline itself. Therefore, their life span is limited by the “habitat” environment itself. Our compatriots (owners of oil refineries and gas stations) actively help him, because of the national Russian mentality they simply cannot help but dilute it with something else, however, and do not add it. All the talk about the price per liter of gasoline is nothing more than a fiction. I think – not many people in Russia disagree with the statement that even if tomorrow you set the price for a liter of rubles at 40, it will still be diluted and underdone.
You just have to come to terms with this – well, historically it happened!

Hence the conclusion – the owners of such machines need to come to terms with the running costs of operating and repairing their cars due to fuel quality.

So – check is off, but error code P 1232 is. The direct interpretation – PRESS REGULATOR – directly points to the pressure regulator. This is a valve mounted on the housing of a high pressure pump, operating in a pulsed mode. The main task is to maintain pressure at the required level, depending on the operating modes of the motor. The ECU valve is controlled, the main sensor – an indicator of the PRESS REGULATOR – is an electronic pressure sensor installed on the same pump casing. For example, NISSAN CEFIRO VQ 25 DD (NEO Di)? NISSAN CEDRIC – similar.

Code P 1232 is one – but its interpretation can be completely different. That this is a regulator or a pump can only be confirmed after diagnosis, not only by the scanner.

Nissan Neo Di - Error P 1232 2

photo 1 – pressure sensor on the fuel pump housing

The notorious PRESS REGULATOR, the solenoid on the fuel pump housing (photo 2):

Nissan Neo Di - Error P 1232 3

For convenience (it should be noted) the connectors have intermediate connectors that are accessible from the outside without disassembling the motor. We are interested in the connector of the pressure sensor and the pressure regulator valve itself .

Nissan Neo Di - Error P 1232 4

The pressure regulator itself has a simple switching circuit – plus 12 volts is supplied to one winding terminal when the ignition is turned on, the second wire in the ECU (red) is controlled by a transistor connected in a circuit with a common emitter (source). Additional diagnostic schemes for the integrity of the valve winding are carried out by the presence of a voltage of 12 volts at this pin – which automatically implies that the winding is whole.

In other words: “including ignition, the ECU checks for a break in the winding”.

You can verify this by simply connecting a voltmeter to the red wire.

The code P 1232 can be recorded immediately after engine start, and can be recorded in the ECU memory after a couple of days of operation. What is wrong – a valve or a pump – is accurately determined after measuring pressure. This can be done with a voltmeter. We connect the voltmeter to the middle terminal of the pressure sensor (black connector), connect the oscilloscope to the red wire (white connector) of the pressure regulator.

We start the engine – the pulse sequence should be observed on the oscilloscope display:

Nissan Neo Di - Error P 1232 5

If it is not there, and the voltage onboard is present at this pin, then we switch the oscilloscope to trigger mode for a single start, reset the counter after turning on the ignition, and start the engine. A record of the freeze frame of the pulse sequence appears on the screen – it means the ECU is working. If the signal disappears later – this is a consequence of a control error and not the ECU .

Nissan Neo Di - Error P 1232 6

And also data stream (if there is something):

Nissan Neo Di - Error P 1232 7

A voltage of 1 volt is a pressure of about 1.5-1.9 MPa. Normal readings are 2.5 volts (7 MPa). In this case, the duration of the closed state of PRESS REG is, according to the waveform, about 2 ms .

Lack of regulation and a voltage of 1 volt indicates a direct malfunction of the regulator – its hydraulic part. If the code appears after start-up, replacing the controller solves the issue of a similar malfunction. But there is a second malfunction associated with this code – pump wear, and as a result low pressure. The ECU, based on the readings of the pressure sensor, “tries” to regulate the pressure by controlling the regulator, while the regulation threshold allows. If the duty cycle of the control pulses exceeds a predetermined value – the ECU writes the code P 1232, but this is the pump code, the controller has nothing to do with it. Simply, the pump is not able to provide the required pressure at such duty cycle. This usually manifests itself in motion..

At the same time, the check may not catch fire, but the code will be in memory. Scanner pressure is typically less than 6 MPa (per xx)

The remaining “health” of the pump can be estimated by the pressure and duty cycle sensor on PRESS REG. At the same constant engine speeds, the pressure developed by the pump will be the same for different duty cycles of the control pulses and vice versa. Figuratively speaking – if the pump is worn out, then to achieve such a pressure, the regulator will have to be in the closed state longer (low pulse) to raise the pressure, or the pressure will be lower for the same duration.

It remains to record the oscillograms of the working pressure and the data from the pressure sensor – and there is a pump characteristic. It can be represented by a tabular value (without load) by parameters – revolutions, pressure (by scanner in MPa), by voltage in volts and by pulse duration of press reg in closed state.

SCV, EGR, etc. systems do not work on these motors with P 1232 code and low pressure, which leads to a drop in power and torque. Although outwardly the engine works as usual – but it does not go into the mode of combustion of ultra-lean mixtures (ULCM), with the ensuing consequences and increased fuel consumption.


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