1998 Chevy Blazer

DTC P0452 - FUEL TANK PRESSURE SENSOR LOW VOLTAGE

Circuit Description

Fuel tank pressure sensor responds to changes in fuel tank pressure (or vacuum). Vacuum is considered negative pressure. This information is used in order to detect vacuum decay or an excessive vacuum during EVAP diagnostic routine. Fuel tank pressure sensor signal voltage to VCM varies from a minimum of about 0.1 volt with pressure in fuel tank to greater than 4.0 volts with high vacuum in fuel tank.

Conditions for setting DTC

Fuel tank pressure sensor voltage is less than 0.1 volt for greater than 5 seconds.

Diagnostic Procedures
1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK, then go to next step.
2. Turn ignition on, engine off. Using scan tool, monitor fuel tank pressure sensor reading. If fuel
tank pressure sensor value is within -1.0 to 1.0 in. H2O, go to next step. If fuel tank pressure sensor value is not within -1.0 to 1.0 in. H2O, go to step 4).
3. DTC is intermittent. Check for additional DTCs set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect fuel tank pressure sensor harness connector. Turn ignition on, engine off. Using DVOM, check voltage between fuel tank pressure sensor harness connector 5-volt reference voltage and ground circuit. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 6).
5. Turn ignition off. Using jumper wires, connect jumper between fuel tank pressure sensor 5-volt
reference circuit at harness connector to sensor terminal. Connect jumper between sensor ground circuit at harness connector to sensor terminal. Turn ignition on, engine off. Using DVOM, check voltage between ground and sensor signal circuit. If voltage is 1.3-2.0 volts, go to step 13). If voltage is not 1.3-2.0 volts, go to step 11).
6. Check for open fuel tank pressure sensor in 5-volt reference circuit. If circuit is open, go to step 15). If circuit is okay, go to next step.
7. Check for short to ground in 5-volt reference circuit. If circuit is shorted, go to step 15). If circuit is okay, go to next step.
8. Check 5-volt reference circuit for poor terminal contact at VCM. If problem is found, go to step 15). If terminal connection is okay, go to next step.
9. Check for open in fuel tank pressure sensor ground circuit. If circuit is open, go to step 15). If
circuit is okay, go to next step.
10. Check sensor ground circuit for poor terminal connection at VCM. If problem is found, go to step 15). If terminal connection is okay, go to step 16).
11. Check fuel pressure sensor signal for short to ground. If circuit is shorted, go to step 15). If circuit is okay, go to next step.
12. Check fuel pressure sensor signal terminal connection at VCM. If problem is found, go to step
15). If terminal connection is okay, go to step 16).
13. Check fuel tank pressure sensor for water intrusion, backed out terminal, improper terminal
mating or poor terminal-to-wire connections. If problem is found, go to step 15). If sensor connections are okay, go to next step.
14. Replace fuel tank pressure sensor. After replacing sensor, go to step 17).
15. Repair circuit as necessary. After repairs, go to step 17).
16. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
17. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
18. Check for additional DTCs. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, system is okay.

Diagnostic Aids

Check for damaged harness or poor connection at VCM or fuel tank pressure sensor.

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VCM = Vehicle Control Module: located at the right side of engine compartment.

Fuel Pump Pressure Sensor