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Home >> Mazda >> 2024 >> CX-90 Turbo Select >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 2 (On-Board Diagnostic - Pcm (VIN A) (1 Of 4)) >> DTC P0171-00: Fuel Trim System Too Lean (PYUL) >> Function Inspection Using M-MDS

Function Inspection Using M-MDS

WARNING: This page is about a different variant/trim than selected.
P0171-00 (PCM (PYUL)) DIAGNOSTIC PROCEDURE

Step Inspection Results Action
1 PURPOSE: IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA 
  • Is the DTC P0171-00 on freeze frame data?
 Yes Go to the next step.
No Go to the troubleshooting procedure for DTC on freeze frame data.
(See DTC TABLE (PYUL) )
2 PURPOSE: RECORD VEHICLE STATUS WHEN DTC WAS DETECTED TO UTILIZE WITH REPEATABILITY VERIFICATION 
  • Record the freeze frame data/snapshot data.
    NOTE:
    • Recording can be facilitated using the screen capture function of the PC.
 - Go to the next step.
3 PURPOSE: VERIFY IF INPUT SIGNAL TO PCM AFFECTS FUEL INJECTION  Yes Inspect the suspected sensor and related wiring harness.
  • If there is any malfunction:
    • Repair or replace the malfunctioning part.
    • Go to Troubleshooting Diagnostic Procedure to perform the repair completion verification 1.
No Go to the next step.
4 PURPOSE: VERIFY CONNECTOR CONNECTIONS 
  • Start the engine.
  • Access the following PCM PIDs using the M-MDS. (See PID/DATA MONITOR INSPECTION )
    • FUEL_PRES
    • FUEL_PUMP_REQ
    • PRG_DUTY
    • MAF
    • MAP_VOLT
    • IAT2
    • VLV_TIMING_ACT_EX
    • VLV_TIMING_ACT_IN
  • Does the PID value fluctuate when the following connectors are shaken?
    • Fuel pressure sensor
    • Fuel pump control module
    • Purge solenoid valve
    • MAF sensor
    • MAP sensor/IAT sensor No. 2
    • Oil control valve (OCV)
    • Electric variable valve timing motor/driver
    • PCM
 Yes Repair or replace the applicable connector parts.
Go to Troubleshooting Diagnostic Procedure to perform the repair completion verification 1.
No Go to the next step.
5 PURPOSE: VERIFY FUEL PRESSURE (LOW-SIDE) MALFUNCTION 
  • Switch the ignition off.
  • Reconnect all disconnected connectors.
  • Start the engine and warm it up completely.
  • Display the PCM PID [FUEL_PRES] using the M-MDS. (See PID/DATA MONITOR INSPECTION )
  • Is the [FUEL_PRES] PID value approx. 10 MPa {102 kgf/cm2, 1450 psi}?
 Yes Go to the next step.
No [FUEL_PRES PID] value is lower than 10 MPa {102 kgf/cm2 , 1450 psi}:
  • Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 1.

    [FUEL_PRES PID] value is higher than 10 MPa {102 kgf/cm2, 1450 psi}:

  • Go to Step 7.
6 PURPOSE: VERIFY FUEL PRESSURE (LOW-SIDE) MALFUNCTION 
NOTE:
  • Verify the fuel pressure on the low pressure side with the operation of the high pressure fuel pump turned off. 
  • Bleed the remaining pressure in the fuel line using the following procedure.
    1. Switch the ignition off.
    2. Disconnect the high pressure fuel pump connector.
    3. Remove the fuel pump relay. (Refer to [RELAY LOCATION ] in Service Information).
    4. Start the engine and wait until the engine stalls.
  • Switch the ignition off.
  • Install the fuel pump relay.
  • Switch the ignition ON (engine off).
  • Display PID [FUEL_PRES] and simulation item [FUEL_PUMP_REQ] using the M-MDS. (See PID/DATA MONITOR INSPECTION ) (See SIMULATION INSPECTION )
  • Turn simulation item [FUEL_PUMP_REQ] on.
  • Is the [FUEL_PRES] PID value 475-555 kPa {4.85-5.65 kgf/cm2, 68.9-80.4 psi}?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 5.
7 PURPOSE: VERIFY IF MALFUNCTION CAUSED BY FUEL INJECTOR IMPROPER OPERATION 
  • Switch the ignition off.
  • Reconnect all disconnected connectors.
  • Start the engine and idle it.
  • Access the following PCM simulation items using the M-MDS: (See SIMULATION INSPECTION )
    • INJ
  • Turn each fuel injector from on to off using the simulation items.
  • Does the vibration during idling worsen?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 7.
8 PURPOSE: VERIFY IF MALFUNCTION CAUSED BY PURGE SOLENOID VALVE IMPROPER OPERATION 
  • Start the engine and idle it.
  • Display the PCM PID [PRG_DUTY] using the M-MDS. (See PID/DATA MONITOR INSPECTION )
  • Is the [PRG_DUTY] PID value normal?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 8.
9 PURPOSE: VERIFY IF MALFUNCTION CAUSE IS MAF SENSOR MALFUNCTION 
  • Start the engine and idle it.
  • Display the PCM PID [MAF] using the M-MDS. (See PID/DATA MONITOR INSPECTION )
  • Is the [MAF] PID value normal?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 10.
10 PURPOSE: VERIFY IF MALFUNCTION CAUSE IS MAP SENSOR MALFUNCTION 
  • Start the engine and idle it.
  • Display the PCM PID [MAP_VOLT] using the M-MDS. (See PID/DATA MONITOR INSPECTION )
  • Is the [MAP_VOLT] PID value normal?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 12.
11 PURPOSE: VERIFY IF MALFUNCTION CAUSE IS INTAKE VALVE TIMING MALFUNCTION 
  • Start the engine and idle it.
  • Access the following PCM PIDs using the M-MDS. (See PID/DATA MONITOR INSPECTION )
    • VLV_TIMING_ACT_IN
    • VLV_TIMING_DSD_IN
  • Depress the accelerator pedal to increase the engine speed.
  • Does the monitor value of the PID item [VLV_TIMING_ACT_IN] conform to the [VLV_TIMING_DSD_IN] PID value?
 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 14.
12 PURPOSE: VERIFY IF MALFUNCTION CAUSE IS EXHAUST VALVE TIMING MALFUNCTION 
  • Start the engine and idle it.
  • Access the following PCM PIDs using the M-MDS. (See PID/DATA MONITOR INSPECTION )
    • VLV_TIMING_ACT_EX
    • VLV_TIMING_DSD_EX
  • Perform the following:
    1. Warm up the engine to allow the engine coolant temperature to reach 80°C {176°F} or more.
    2. Shift to D position and rapidly accelerate the vehicle to 50 km/h {31 mph} (to operate hydraulic variable valve timing control).
    3. Decelerate to idling.
    4. Shift to D position and rapidly accelerate the vehicle to 50 km/h {31 mph} again.
  • Does the monitor value of the PID item

    [VLV_TIMING_ACT_EX] conform to the [VLV_TIMING_DSD_EX] PID value?

 Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 17.
13 PURPOSE: VERIFY IF MALFUNCTION CAUSE IS A/F SENSOR MALFUNCTION  Yes Go to the next step.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 18.
14 PURPOSE: INSPECT FOR OTHER RELATED DTCs 
  • Perform the DTC inspection for the PCM. (See DTC INSPECTION )
  • Are any other DTCs displayed?
 Yes Repair or replace the malfunctioning location according to the applicable DTC troubleshooting.
(See DTC TABLE (PYUL) )
Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 1.
No Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 1.
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