EPA07/10/GHG14 DDEC VI/10 Electronics and Troubleshooting Manual (DDC-SVC-MAN-0084) | 90 SPN 164 (MCM) (EPA10;GHG14) | 90.6 SPN 164/FMI 21 – EPA10 – GHG14

Description	Fuel Rail Pressure Sensor – Drift Low
Monitored Parameter	Fuel Rail Pressure Sensor
Typical Enabling Conditions	Key On & Engine Off
Monitor Sequence	None
Execution Frequency	Once when enabling conditions met
Typical Duration	10 Seconds
Dash Lamps	MIL, CEL
Engine Reaction	Derate 25%
Verification	Key On & Engine Off

Check as follows:

1. Disconnect the fuel rail pressure sensor.

1. Inspect the fuel rail pressure sensor connector and harness connector for signs of damage: bent, spread, broken, unseated (pushed out) or corroded pins, signs of water intrusion or damaged wiring near the connector.
   1. If signs of damage are present, repair as necessary.
   1. If no signs of damage are present, Go to step 3.

1. Turn the ignition ON (key ON, engine OFF).

1. Measure the voltage between pins 1 and 3 of the fuel rail pressure sensor harness connector.
   1. If the voltage is between 4.5 and 5.5 volts, Go to step 6.
   1. If the voltage is not between 4.5 and 5.5 volts, Go to step 5.

1. Measure the voltage between pin 3 of the fuel rail pressure sensor harness connector and battery ground.
   1. If the voltage is between 4.5 and 5.5 volts, repair the wire between pin 1 of the fuel rail pressure sensor harness connector and pin 102 of the MCM 120-pin connector.
   1. If the voltage is not between 4.5 and 5.5 volts, repair the wire between pin 3 of the fuel rail pressure sensor and pin 58 of the MCM 120-pin connector.

1. Turn the ignition OFF.

1. Disconnect the MCM 120-pin connector.

1. Inspect the MCM 120-pin connector and harness connector for signs of damage; bent, spread, broken, unseated (pushed out) or corroded pins, signs of water intrusion or damaged wiring near the connector.
   1. If signs of damage are present, repair as necessary.
   1. If no signs of damage are present, Go to step 9.

1. Measure the resistance between pin 2 of the fuel rail pressure sensor harness connector and pin 78 of the MCM 120-pin connector.
   1. If the resistance is less than 5 ohms, Go to step 10.
   1. If the resistance is greater than 5 ohms, repair the wire between pin 2 of the fuel rail pressure sensor harness connector and pin 78 of the MCM 120-pin connector.

1. Measure the resistance between pin 3 of the fuel rail pressure sensor harness connector and pin 58 of the MCM 120-pin connector.
   1. If the resistance is less than 5 ohms, Go to step 11.
   1. If the resistance is greater than 5 ohms, repair the wire between pin 3 of the fuel rail pressure sensor harness connector and pin 58 of the MCM 120-pin connector.

1. Measure the resistance between pins 1 and 2 of the fuel rail pressure sensor harness connector.
   1. If the resistance is greater than 10K ohms, Go to step 12.
   1. If the resistance is less than 10K ohms, repair the short in the wires between pins 1 and 2 of the fuel rail pressure sensor harness connector.

1. Reconnect the MCM 120-pin harness connector.

1. Turn the ignition ON (key ON, engine OFF).

1. Measure the voltage between pins 1 and 3 of the fuel rail pressure sensor harness connector.
   1. If the voltage is between 4.5 and 5.5 volts, replace fuel rail pressure sensor. 
   1. If the voltage is not between 4.5 and 5.5 volts, repeat the above procedure. If the results are the same, replace the MCM module.