Fuel Level Input (FLI) Circuit Malfunction

DTC P0457 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0460	FUEL LEVEL INPUT (FLI) CIRCUIT MALFUNCTION
DETECTION CONDITION	PO460 indicates a Fuel Level Input (FLI) circuit malfunction due to a low/high FLI circuit input to the PCM or a mechanically stuck Fuel Pump (FP) module.
POSSIBLE CAUSE	Empty fuel tank. Fuel pump (FP) module stuck open. Incorrectly installed fuel gauge. Damaged instrument cluster. CASE GND circuit open. FLI shorted to VPWR. Damaged PCM. Overfill fuel tank. Fuel pump (FP) module stuck closed. Damaged fuel gauge. FLI circuit open. FLI circuit shorted to CASE GND or PWR GND. CASE GND shorted to VPWR.
HINT	FLI Description Indicates the fuel level in the fuel tank. Hard wire signal input to the PCM from the fuel pump (FP) module.
Courtesy of MAZDA MOTORS CORP.

DTC PO460 INSPECTION

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	Go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test.
2	DTC P0460: CHECK FUEL TANK LEVEL Key ON, Engine OFF (KOEO). Observe and record fuel gauge reading. Access FLI PID using NGS Tester. Are both the fuel gauge and the FLI PID indicating between one third (33% on FLI PID) and three quarters (75% on the FLI PID) filled?	Yes	Go to step 4.
2		No	Key OFF. Inspect fuel tank for leaks. Repair fuel tank if necessary. Check for damaged fuse 11 for the fuel pump (FP) to fuel gauge circuit. For a damaged fuse without a DTC P0460: Check for CASE GND short to VPWR circuit. For fuel gauge inoperative without a DTC P0460: See TEST A: FUEL GAUGE INACCURATE in Instrument Panels article in Accessories & Equipment . For DTC P0460: Go to next step.
3	CHECK FOR INADEQUATE FUEL LEVEL Key ON, Engine OFF (KOEO). Observe both the fuel gauge and FLI PID while performing the following: If fuel level is under one third (33% on FLI PID), add 2 to 3 gallons (7.57 to 11.36 liters) of fuel to the fuel tank. If fuel level is over three quarters (75% on FLI PID), drain 2 to 3 gallons (7.57 to 11.36 liters) of fuel from the fuel tank. Did either the fuel gauge or FLI PID indicate a movement upward or downward as the fuel was either added or taken away?	Yes	Drive vehicle and rerun PCM Quick Test. If DTC P0460 is still present, go to next step.
3		No	Key OFF. Go to step 5.
4	CHECK FLI CIRCUIT VOLTAGE Key ON, Engine Running (KOER). Access FLI V PID using NGS Tester. Is voltage or FLI V PID reading between 1.23 and 2.25 V?	Yes	For DTC 460, fault is intermittent. See TEST 4: INTERMITTENT . If here from symptom troubleshooting, replace fuel gauge. Go to step 12.
4		No	Go to next step.
5	CHECK FUEL PUMP MODULE RESISTANCE Key OFF Disconnect fuel pump (FP) module. Measure resistance between FLI and CASE GND pins on the FP module (at pigtail). Is the resistance between 15 and 160 ohms?	Yes	Go to next step.
5		No	Check for stuck fuel level float on fuel pump (FP) module. Repair as necessary. If free movement is present, replace fuel pump. See FUEL PUMP in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance . Go to step 12.
6	CHECK FLI CIRCUIT VOLTAGE AT FUEL PUMP MODULE Disconnect the instrument cluster connector (C-125) to the fuel gauge. Key On Engine OFF (KOEO). Measure voltage between FLI circuit at the fuel pump harness connector and battery negative post. Is the voltage greater than 5 V?	Yes	Go to next step.
6		No	Go to step 8.
7	CHECK FLI CIRCUIT FOR SHORT TO VPWR IN HARNESS Key OFF. Disconnect PCM. Key ON, Engine OFF (KOEO). Measure voltage between FLI at the fuel pump harness connector and battery negative post. Is the voltage greater than 10.5 V?	Yes	Repair short circuit. Go to step 12.
7		No	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 12.
8	CHECK FLI CIRCUIT FOR SHORT TO PWR GND IN HARNESS Key OFF. Disconnect PCM. Install Breakout Box, leave PCM disconnected. Measure resistance between PCM test pin 12 (FLI) and battery negative post. Is the resistance greater than 10K ohms?	Yes	Go to next step.
8		No	Repair short circuit. Go to step 12.
9	CHECK FLI CIRCUIT FOR SHORT TO CASE GND IN HARNESS Measure resistance between FLI and CASE GND circuits at the fuel pump (FP) module. Is resistance greater than 10K ohms?	Yes	Go to next step.
9		No	Repair short between FLI and CASE GND. Go to step 12.
10	CHECK FLI CIRCUIT FOR OPEN IN HARNESS If here from Symptom Troubleshooting, measure resistance of FLI circuit between PCM test pin 12 and fuel pump (pigtail) harness connector. Measure resistance of FLI circuit between PCM test pin 12 and pin 12 of C-215 at the instrument cluster. Is each resistance less than 10.0 ohms?	Yes	Go to next step.
10		No	Repair open circuit. Go to step 12
11	CHECK CASE GND CIRCUIT FOR OPEN IN HARNESS Measure resistance of CASE GND between FP module connector and battery. Is the resistance less than 10.0 ohms?	Yes	Replace fuel gauge or repair as necessary if here from Symptom Troubleshooting. See GAUGES in Instrument Panels article in Accessories & Equipment . If DTC P0460 is still present, replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 12.
11		No	Repair open circuit. Go to step 12.
12	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using NGS tester generic OBD-II function. Perform PCM Quick Test. Is same DTC present?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Repeat PCM Quick Test.
12		No	If any other DTC is present, go to applicable DTC inspection. If no DTC is present, troubleshooting complete.