MIL ON DTC P0451 Stored in Memory
No: 19/07/97/NASRef: WSM section 19
Issue: 2
Date: 12/19/97
PRIDE V 1-17
EVAPS Fuel *Tank* Pressure Sensor
Fault P0451
AFFECTED VEHICLE RANGE
DISCOVERY (LJ) ALL ADVANCED EVAPS EQUIPPED
Changes are noted by asterisks.
SITUATION:
MIL ILLUMINATION, CODE P0451
* Vehicles equipped with Advanced EVAPS may experience a MIL illumination and a Fuel Tank Pressure Misfire codes (P0300, 301, etc.) may also be present. These conditions could be caused problems in the Fuel Pressure Sensor circuit, and because the fuel tank pressure sensor shares reference voltage with the Throttle Position Sensor (TPS), a circuit fault can cause the reference voltage to change, thus affecting output of the TPS Connectors are a common source of troubles in electrical systems. Technicians are advised to check particularly the fuel tank pressure sensor connector Note that dirty, corroded, or damaged connectors cannot be repaired or cleaned; they must be replaced.*
RESOLUTION:
REPLACE FUEL PUMP ASSEMBLY AND WIRING HARNESS
If it is found that Code P0451 is due to a poor connection at the connector to the fuel *tank* pressure sensor, the fuel pump assembly is to be replaced. Additionally the wire harness connecting the sensor to the body harness must also be replaced.
CAUTION:
Do not use any type of contact cleaner, preservative or stabilant in an attempt to rectify the poor connection. Use of any of these materials will void the manufacturer's warranty.
Use the following procedure to diagnose and repair this problem. If the poor connection has affected the TPS reference voltage the engine adaptations and IACV steps will have to be reset.
NOTE:
The repairs outlined in this TIB are to be performed to resolve customer complaint of the symptoms described.
PARTS INFORMATION:
ESR3209 .............. Fuel Pump Assembly Qty 1
YMT100050 ........... Wiring harness Qty 1
WARRANTY CLAIMS:
19.22.98 ............... Time: 0.8 hrs. hrs.
TestBook Diagnosis Code Retrieval and Drive Cycle "A". FAX DTCR
19.22.0451 ........... Time: 0.05
Code P0451
19.10.89.28 .......... Time: 0.2 hrs.
Replace wiring harness
19.45.03 .............. Time: 0.75 hrs
Replace Fuel Pump Assembly
COMP CODE: 7U8T
Normal warranty policy and procedures apply
REPAIR PROCEDURE
DIAGNOSIS
1. Install TestBook and retrieve P-Codes.
2. Complete a DTCR complete with freeze-frame data and FAX to LRNA.
3. Check reference voltage for fuel tank pressure sensor by backprobing connector C1033 pin 4 of the GEMS unit with the key on and the engine off.
*4. If voltage present is less than 5 volts, the fuel tank pressure sensor might be shorted to ground. Check the connector for the fuel tank pressure sensor.*
5. Following directions in the WSM, remove carpet in rear of vehicle; remove 6 screws from access panel over fuel pump and gauge sender unit.
6. Pull connector from fuel tank pressure sensor (Figure 1) and examine connector and sensor for poor connection.
7. Recheck voltage at GEMS ECM, if voltage is now correct, the problem is with poor connection at the fuel tank pressure sensor pulling the reference voltage low.
REPAIR
8. Following directions in WSM. remove fuel pump and gauge sender unit.
1. Replace fuel tank pressure sensor wiring harness.
2. Install new fuel pump and gauge sender unit.
CAUTION:
Do not use any type of contact preservative. Use of these materials will void the manufacturer's warranty.
3. Before connecting the new harness to the fuel tank pressure sensor, check Pin 3 (black) of the new harness for continuity to ground.
4. Connect wiring harnesses and fuel hoses and clamp securely.
5. With the fuel filler cap removed, key on and engine off, check the wires in the following connectors on the GEMS ECM for the following:
^ Connector C1033, Pin 4 (Red)= 5 volts.
^ Connector C1017, Pin 30 (Green/Pink)= 3.0 volts 1.16 volt.
6. Refer to the ETM to repair any problems found with the wiring.
7. Reinstall all interior components following instructions in the WSM.
RESET ENGINE ADAPTATION
1. Using TestBook clear any codes that have been set.
2. Go to the adaptation screen (SUBSYSTEMS TESTS/ECM OPTIONS/RESET ADAPTATIONS) and follow instructions to reset engine adaptation and IACV to 20-25 steps.
3. Perform Drive Cycle "A" to confirm repair.