Trouble code p0090 fuel pressure regulator 1control circuit

[Towcobbs]

My 14 plate rapid hatchback has the engine management light on with trouble code p0090 and I can not find any info relating to this,so far the high pressure pump and regulator on the end of the fuel rail have been replaced. Also the pump in the tank has been replaced this a 1.2 tsi 77kw engine model. I am beginning to think this a wiring or ECU problem my local garages have no idea can anybody help me please. I should add that you can delete the code and drive for about half a mile before it comes on again.

[Breezy_Pete]

If you can tell me the engine code I may be able to help by looking at wiring diagrams.  Can be found on vehicle data sticker on boot floor, copy in service book etc.

[Towcobbs]

The engine code is CBZB the 77kw of 105bhp 4 cylinder version. Cheers

[RicardoM]

Common causes of OBD2 error code P0090
Probable causes include a faulty fuel pressure regulator, a faulty fuel pump, a clogged fuel filter, a low fuel pressure, a faulty fuel pump relay, or a faulty sensor. Damaged or corroded relevant electrical cables, short-circuits and / or electrical connectors are also common causes of this code being stored.

 

Diagnosis
The electronic fuel pressure regulator is used to maintain a constant fuel pressure. Power is supplied to the controller via the PCM module (or the fuel delivery module along with the PCM), and the fuel pressure is monitored by the PCM via the pressure sensor.

Because the fuel supply pressure sensor inputs data to the PCM, the voltage variations (from the PCM output to the electronically controlled fuel pressure regulator) command the fuel pressure regulator to restrict or allow fuel as needed. Other input signals from different engine sensors are also used by PCM to develop a fuel delivery strategy.

As the voltage in the PCM increases, the actuator of the fuel pressure regulator allows the pressure in the fuel pump and, because the voltage (from the PCM) is too low, the fuel pressure is limited. Several tools will help to successfully diagnose this code.

A proper OBD-II scanner (or a code reader), a digital voltmeter / ohmmeter and a fuel pressure gauge will be very helpful in successfully making a diagnosis. Start with a visual inspection of all harnesses and connectors. Repair or replace damaged, disconnected or corroded harness, connectors and components as appropriate. Re-test the system after the repairs have been successfully completed. If all cables, connectors, and components (including fuses) of the system appear in normal order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes.

This information can be extremely useful in diagnosing intermittent conditions that may have contributed to the storage of this code. Continue to delete the code and restart the car to see if it reappears. This will help you determine whether or not the dysfunction is intermittent.

Make sure the engine is filled to the appropriate level with the appropriate engine oil. After the codes are cleared, try driving the vehicle to see if the code reappears. If the code does not reappear immediately, you may have an intermittent condition.

Intermittent conditions may prove to be quite a challenge to diagnose and, in extreme cases, may worsen before a correct diagnosis can be made. Connect the pressure gauge to the appropriate location according to the manufacturer's recommendations and turn the key to the ON position. Follow the fuel pressure and compare your results with the manufacturer's specifications found in the service manual. If the fuel pressure maintains a level that meets the manufacturer's specifications, you may suspect a faulty fuel pressure sensor or PCM. If the fuel pressure is insufficient, there is probably a problem with the fuel pump or fuel filter. If the vehicle does not start, check the fuel pressure with a pressure gauge. Compare the readings with the manufacturer's specifications.

If the fuel pressure is found to be too low, check for fuel in the vehicle. Once you check and find that it is sufficient fuel, listen if the electric fuel pump is working properly. If the fuel pump is operating normally and the vehicle does not start, you may suspect a clogged fuel filter or a problem with the fuel injector circuit (including PCM). If the fuel pump does not sound running, use a rubber hammer to easily reach the bottom of the fuel tank while someone else is trying to start the car. If the vehicle starts while you lightly touch the tank, it means that you have a defective fuel pump (this is the simplest test method).

 

If the vehicle does not start, check the battery voltage at the fuel pump connector. If there is no voltage, follow the fuel pump circuit to the fuse panel, fuel pump relay and / or PCM.

 

Detailed Diagnosis

Many vehicles equipped with OBD-II systems use a fuel pressure sensor to monitor its pressure. The sensor is of variable resistance. As the fuel pressure increases, the sensor resistance decreases, allowing the system voltage to increase. When the fuel pressure drops, the sensor resistance increases, causing the system voltage to drop. PCM reads these variations of system voltage as fuel pressure and reacts accordingly. You will need a scanner or a code reader and a digital ohmmeter to successfully diagnose this code.

Start by disconnecting the electrical connector from the pressure sensor and checking the reference voltage. This is usually 5 volts, but consult the manufacturer's service manual to be sure. If there is a 5-volt signal, with the ignition switch in the operating position, then check the sensor ground for the sensor. If both the reference signal and the ground signal are present, test the resistance of the sensor using the manufacturer's pressure / resistance diagram. Compare your conclusions with the manufacturer's specifications and replace the sensor if it does not meet the requirements. If the sensor and sensor voltage are within acceptable specifications, disconnect the PCM electrical connector and the resistance of the test circuit between the sensor and PCM.

Repair or replace system circuits and components and retest the system. If you check all system circuits and sensors, you may suspect a faulty PCM, but keep in mind that PCM failures are rare and that PCM replacement will require reprogramming.

If the fuel pressure regulator does not meet the manufacturer's specifications, replace it then remove the codes and try to drive the vehicle to ensure that the repair has been completed successfully. If testing the fuel pressure regulator shows that it complies with the manufacturer's specifications, disconnect the electrical connectors from the regulator and check the reference voltage. Then connect the electrical connector back to the fuel pressure regulator and monitor the signal cable voltage using a digital voltage ohmmeter. Compare your conclusions with the manufacturer's specifications and replace the fuel pressure regulator if the signal voltage does not match.

If the PCM input signal proves to be within the manufacturer's specifications and the scanner has a contradictory note, disconnect the connector from the fuel pressure regulator, the fuel pressure sensor and all related control modules. Perform a continuity and resistance test on all circuits and compare the findings with the manufacturer's specifications. Repair or replace system circuits, connectors and / or components as required and delete codes.

Try driving the vehicle to ensure a successful repair. If all system circuits meet manufacturer's specifications, you may suspect a faulty fuel delivery controller or PCM.

[Breezy_Pete]

Fuel pressure sensor G247 pin 3, yellow/grey wire is the 5V supply to the fuel pressure sender (seems to start at engine ECU pin 29 as a red/blue wire) . Brown is earth.

Pin 2, yellow/blue goes to engine ECU pin 40. Check those out for continuity and short-circuits to each other and chassis.

 

Fuel pressure regulating valve, N276, has a white/yellow wire going to engine ECU pin 19 and a blue red wire feeding power from fuse 32 (15 amp) in the dashboard fuseholder. Check fuse, check continuity and for short circuits.

 

I'm afraid I don't know the physical locations of these two things, hopefully google can help with that.

 

Top work from @RicardoM above, gonna give him a like for that one...

 

[MickA]

Have you had the battery condition checked?

[Towcobbs]

Yes it's a new battery. Holding 13volts.

[Towcobbs]

Thanks for your help do far I checked the voltage to the sensor on the fuel rail it is 4.9 volts and the earth has continuity I will check to the ECU tomorrow. There is no way of checking the fuel pressure we are using a very expensive autel diagnostic and there is no live data for fuel pressure. 

[Towcobbs]

Thanks for all your help I followed all the wires checked continuity  they were all good so I went to the fuse box to fuse 32,except there was no fuse 32. I put a new fuse in cleared the codes and it cured the fault,I found the fuse under the mats so I checked them all and several needed pushing in. So thanks again.

[Breezy_Pete]

 

[RicardoM]

Wow, you drove it till the fuses started to fall out...🙂

Now really, that is a first for me. Somebody in the Skoda Rapid quality assurance line should answer for that. Fuses don't just fall off.