FC CONTROL SYSTEM, Diagnostic DTC:P1DC1-450

DTC Code	DTC Name
P1DC1-450	Low-range Hydrogen Pressure Too High

DESCRIPTION

The hydrogen system of the FC system feeds the FC stack with hydrogen, so that the FC stack can generate power. The low-range pressure circuit is located after the hydrogen injectors, and pressure applied to the circuit is regulated by the hydrogen injectors to an appropriate level for FC stack power generation.

If the regulated low-range hydrogen pressure exceeds a threshold, the FC control ECU interprets it as a higher pressure limit error, and sets this DTC.

For the circuit diagram, refer to DTC P1DC0-450.

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DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate
P1DC1-450	Low-range Hydrogen Pressure Too High	Low-range hydrogen pressure has exceeded a threshold. This malfunction detection is active all the time. (1 trip detection logic)	FC stack assembly (hydrogen injector, low-range hydrogen pressure sensor)	Master Warning Light: Comes on

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

P1DC1-450

Low-range Hydrogen Pressure Too High

Low-range hydrogen pressure has exceeded a threshold. This malfunction detection is active all the time.

(1 trip detection logic)

FC stack assembly (hydrogen injector, low-range hydrogen pressure sensor)

Master Warning Light: Comes on

Tech Tips

If low-range hydrogen pressure increases despite hydrogen injectors being not forced to open, it is suspected that hydrogen injectors are malfunctioning.

Detection timing
Vehicle Condition	FC shutdown (power switch on (IG))	FC startup process	FC intermittent operation	FC is generating power (vehicle is in stationary)	FC is generating power (vehicle is traveling)	FC shutdown process
Data List "FC Mode"	FC Shutdown	FC Startup Process	FC Working			FC Shutdown Process
Data List "FC Intermittent Operation"	OFF		ON	OFF		OFF
DTC Detection	○	○	○	○	○	○

Related Data List
DTC No.	Data List
P1DC1-450	Smoothed Value of Low-range Hydrogen Pressure Target Low-range Hydrogen Pressure

The following items can be helpful when performing repairs:

Data List

Tank Shut Valve 1 Driving Request
Tank Shut Valve 2 Driving Request
Hydrogen Injector 1 Injection Request
Hydrogen Injector 2 Injection Request
Hydrogen Injector 3 Injection Request
Motor Room Side Hydrogen Detector Density
Tank Side Hydrogen Detector Density

Common Data List items for FC inspection

Vehicle Speed
Shift Sensor Shift Position
Accelerator Degree
Ready
FC Mode
FC Intermittent Operation
FC Voltage before Boosting
FC Current
Target Hydrogen Pump Revolution
Hydrogen Pump Revolution
Target FC Stack Air Pressure (FC Stack Inlet)
Smoothed Value of FC Stack Air Pressure (FC Stack Inlet)
Target Mass Air Flow Value
Mass Air Flow Value
Target Air Compressor Revolution
Air Compressor Revolution
Target FC Stack Coolant Temperature (FC Stack Outlet)
Smoothed Value of FC Stack Coolant Temperature (FC Stack Outlet)
Exhaust Drainage Valve Driving Request

Related Active Test
DTC No.	Active Test
P1DC1-450	Hydrogen Injector

Note

If any one of the hydrogen injectors does not close, malfunctioning injectors cannot be identified through an Active Test.

CAUTION / NOTICE / HINT

CAUTION:

Work procedures must be performed in an area with good ventilation (airflow) where hydrogen gas will not accumulate, and flames or other things that could act as ignition sources must not be present.
Accumulated hydrogen gas could ignite, resulting in a serious accident.

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Note

When the vehicle is parked with the power switch off, if the FC control ECU judges that the FC stack temperature will go below 0°C (32°F), it activates the FC air compressor, hydrogen pump and FC cooling water pump for a maximum of 180 seconds and drains water from the FC stack assembly. When performing inspection or repairs with the power switch off (not on (IG) or on (READY)), disconnect the cable from the negative (-) auxiliary battery terminal before performing work (If the auxiliary battery voltage is needed to conduct inspection, warm up the FC system beforehand).

Tech Tips

After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output.

Turn the power switch on (READY) with the shift lever in P, and check the Data List that "FC Mode" is FC Working and "FC Intermittent Operation" is OFF. Then, wait 2 minutes or more.
Check that the "Smoothed Value of Low-range Hydrogen Pressure" in the Data List is 280 kPa(abs) or less.

After completion of repair, check that no hydrogen leaks from the hydrogen system components with a hydrogen gas detector.

PROCEDURE

CHECK DTC OUTPUT

Note

The freeze frame data is cleared when DTCs are cleared. Be sure to make a note of necessary data in advance.

Connect the GTS to the DLC3.
Turn the power switch on (IG).
Turn the GTS on.
Enter the following menus: Powertrain / FC / Trouble Codes.

Check for DTCs.

Powertrain > FC > Trouble Codes

Result

Result	Proceed to
No DTCs are output, or DTCs except the ones in the table below are also output.	A
Any of the following DTCs are also output.	B

Malfunction Content	Relevant DTC
Sensor and Actuator Circuit Malfunction	P1D9C-450	Hydrogen Injector No. 1 Circuit Low
	P1D9D-450	Hydrogen Injector No. 1 Circuit High
	P1DA2-450	Hydrogen Injector No. 2 Circuit Low
	P1DA3-450	Hydrogen Injector No. 2 Circuit High
	P1DA7-450	Hydrogen Injector No. 3 Circuit Low
	P1DA8-450	Hydrogen Injector No. 3 Circuit High
	P1DBC-450	Low-range Hydrogen Pressure Sensor Circuit Low
	P1DBD-450	Low-range Hydrogen Pressure Sensor Circuit High

Tech Tips

DTC P1DC1-450 may be set due to problems that cause the DTCs shown above to be output. If such happens, troubleshoot the suspected area(s) corresponding to the output DTC(s) in order starting with the listed DTCs shown in the table above.
If DTC P1E40-450 or P1E41-450 is output together with P1DC1-450, hydrogen may have leaked from the low-range hydrogen pressure components, or hydrogen may have been discharged by the low-range hydrogen pressure relief valve. After completion of repair, check for hydrogen leaks in the FC stack assembly.

Turn the power switch off.

GO TO DTC CHART Click here

CLEAR DTC

Connect the GTS to the DLC3.
Turn the power switch on (IG).
Turn the GTS on.
Enter the following menus: Powertrain / FC / Trouble Codes.
Clear the DTCs.

Powertrain > FC > Clear DTCs

Turn the power switch off and wait for 3 minutes or more.

Result

Proceed to
NEXT

READ VALUE USING GTS

Connect the GTS to the DLC3.
Turn the power switch on (IG).
Turn the GTS on.

Enter the following menus: Powertrain / FC / Data List / FC Mode, Hydrogen Injector 1 Injection Request, Hydrogen Injector 2 Injection Request, Hydrogen Injector 3 Injection Request, Tank Shut Valve 1 Driving Request, Tank Shut Valve 2 Driving Request, Smoothed Value of Low-range Hydrogen Pressure

Powertrain > FC > Data List

Tester Display
FC Mode
Hydrogen Injector 1 Injection Request
Hydrogen Injector 2 Injection Request
Hydrogen Injector 3 Injection Request
Tank Shut Valve 1 Driving Request
Tank Shut Valve 2 Driving Request
Smoothed Value of Low-range Hydrogen Pressure

Using the GTS snapshot, record the values of the Data List items listed above.
Turn the power switch on (READY) and check the Data List that "FC Mode" is FC Working.

Tech Tips

If DTCs are set and FC Working is disabled, record data from when the power switch is turned on (IG) until the FC system shuts down.

Check the "Smoothed Value of Low-range Hydrogen Pressure" with the following conditions met.

FC Mode = FC Startup Process*
Tank Shut Valve 1 Driving Request = ON
Tank Shut Valve 2 Driving Request = ON
Hydrogen Injector 1 Injection Request = OFF
Hydrogen Injector 2 Injection Request = OFF
Hydrogen Injector 3 Injection Request = OFF

*: If the FC system can be activated, check the Data List value with the "FC Mode" in FC Working.

Figure 1. Reference example

Result

Result	Proceed to
"Smoothed Value of Low-range Hydrogen Pressure" increases when the "Hydrogen Injector Injection Request" in the Data List is OFF.*	A
Other than above	B

*: The hydrogen injector is malfunctioning

Turn the power switch off.

REPLACE FC STACK ASSEMBLY Click here

CHECK FOR INTERMITTENT PROBLEMS Click here