Ford F150 Pickup. Instruction - part 1476

Fig. 190: Accelerator Pedal Position Sensor Voltage 
Courtesy of FORD MOTOR CO. 

Fig. 191: Identifying Accelerator Pedal Position Sensor Circuits & Connector Terminals 
Courtesy of FORD MOTOR CO. 

Diagnostic Aids 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

This system test is intended to diagnose the following: 

z

ETC Accelerator Pedal Position (APP) sensor note: the APP sensor and pedal are an assembly.  

z

Sensor harness circuits: ETC RTN, SIG RTN, ETC REF, APP1, APP2 and APP3.  

z

Powertrain Control Module (PCM).  

Testing 

1) For KOEO, KOER & Continuous Memory DTCs P2121-P2123, P2126-P2128 & P2131-P2133: 
Check Accelerator Pedal Assembly For Binding 
 
These DTCs indicate that one of the Accelerator Pedal Position sensor fault flags is set for sensor by the 
PCM, indicating that signal is out of the normal self-test operating range. Possible causes are: 

z

APP sensor defective.  

z

APP sensor is open, or shorted to ground or power.  

z

APP sensor assembly is binding.  

z

APP sensor signal circuits shorted together.  

z

Damaged PCM.  

The following steps should be taken in order due to the nature of the Electronic Throttle Control system:  

A. These DTCs effect system operation and must be repaired first: P0102, P0103, P0122, P0123, 

P0222, P0223, P0320, P0715, P0720, P0500 and P2135. See DIAGNOSTIC TROUBLE CODE 
DEFINITIONS.  

B. These DTCs must be repaired next due to the nature of the system: P2121, P2122, P2123, P2126, 

P2127, P2128, P2131, P2132 and P2133. Go to next step.  

C. If DTCs P2111 or P2112 are present, go to TEST DV step 1).  

D. If DTC U0300 is present, see appropriate BODY CONTROL MODULES article in 

ACCESSORIES & EQUIPMENT.  

Turn ignition switch to ON position. Depress accelerator pedal slowly to the floor and release. Does the 
accelerator pedal move to the floor and back without sticking? If yes, go to next step. If no, isolate and 
repair binding, or replace pedal/sensor assembly. 

2) Check APP Sensor Signal Voltage Ranges 
 
Turn ignition switch to ON position. Access and monitor APP sensor 1, 2, and 3 PIDS. Depress 
accelerator pedal slowly to the floor and release. Are the open and closed voltages within the specified 
table ranges? See APPS SIGNAL VOLTAGES table. If yes, go to step 9). If no, for DTCs P2121 and 
P2122 alone, DTCs P2126 and P2127 alone, or DTCs P2131 and P2132, go to step 4). For any 
combination of these groups, go to next step. 

APPS SIGNAL VOLTAGES 

Pedal Position

APP1

APP2

APP3

Closed Throttle

4.0-4.2 V

1.4-1.6 V

0.8-1.0 V

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

3) Check For VREF Voltage At The APP Sensor Harness Connector 
 
Turn ignition switch to OFF position. Disconnect APP sensor harness connector. Turn ignition switch to 
ON position. Measure voltage between ETC REF and ETC RTN circuits, and then between ETC REF 
and SIG RTN circuits at the APP sensor harness connector. See Fig. 191. Measure voltage between the 
other ETC REF and ETC RTN, and then between the other ETC REF and SIG RTN at the APP sensor 
harness connector. Are both voltages between 4 and 6 volts? If yes, go to next step. If no, go to TEST C, 
step 1). 

4) Check The APP Sensor Circuits For Open In Harness 
Accelerator Pedal Position sensor fault flag is set for sensor by the PCM, indicating that signal is out of 
the normal self-test operating range. Possible causes of DTCs are: 

z

APP sensor defective.  

z

APP sensor is open, or shorted to ground or power.  

z

APP sensor signal circuits shorted together.  

z

Damaged PCM.  

For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 
circuit, and for DTCs P2131 and P2132, check only the APP3 circuit. Turn ignition switch to OFF 
position. Disconnect PCM harness connector. Measure resistance of the APP2 and APP3 circuit, between 
the APP sensor connector and PCM harness connectors. Are the resistances less than 5 ohms? If yes, for 
DTCs P2123, P2128 and P2133, go to next step. For DCTs P2121, P2122, P2126, P2127, P2131 and 
P2132, go to step 7). If no, isolate and repair open circuit. 

5) Check APP Sensor Harness For Signal Short To The ETCREFS In Harness 
Accelerator Pedal Position sensor is out of range high. Possible causes of DTCs are: 

z

APP sensor is defective.  

z

APP sensor assembly is binding.  

z

APP sensor harness is shorted to power.  

z

Damaged PCM.  

For DTCs P2121 and P2123, check APP1 circuit only, for DTCs P2126 and P2128 check APP2 circuit 
only, and for DTCs P2131 and P2133 check APP3 circuit only. Disconnect PCM and APP sensor harness 
connectors. Measure resistances between the APP1, APP2 and APP3, and the ETC REF at the APPS 
harness connector. Measure resistances between the APP1, APP2 and APP3, and the other ETC REF at 
the APPS harness connector. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, 
isolate and repair short circuit. 

Wide Open Throttle

0.8-1.0 V

3.8-4.0 V

3.2-3.4 V

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

NOTE:

For additional testing information, see DIAGNOSTIC AIDS.

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline

  

6) Check The APP Sensor Circuits For Short To PWR 
 
For DTCs P2121 and P2123, check APP1 circuit only, for DTCs P2126 and P2128, check APP2 circuit 
only, and for DTCs P2131 and P2133 check APP3 circuit only. Disconnect PCM and APP sensor harness 
connectors. Turn ignition switch to OFF position. Measure resistance between the APP1, APP2 and 
APP3, and battery power at the APP sensor harness connector. Are the resistances greater than 10 
k/ohms? If yes, go to next step. If no, isolate and repair short circuit. 

7) Check APP Sensor Circuits For Short To SIG RTN & ETC RTN 
 
For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 
circuit, and for DTCs P2131 and P2132, check only the APP3 circuit. Disconnect PCM and APP sensor 
harness connectors. Measure resistance between APP1, APP2 and APP3 circuits, and SIG RTN circuit at 
the APP sensor harness connector. Measure resistance between APP1, APP2 and APP3 circuits, and ETC 
RTN circuit at the APPS sensor harness connector. Are the resistances greater than 10 k/ohms? If yes, for 
DTCs P2121, P2122, P2126, P2127, P2131 and P2132, go to next step. For all others, go to step 9). If no, 
isolate and repair short circuit. 

8) Check The APP Sensor Circuits For Short To GND 
 
For DTCs P2121 and P2122, check only APP1 circuit, for DTCs P2126 and P2127, check only APP2 
circuit, and for DTCs P2131 and P2132 check only the APP3 circuit. Turn ignition switch to OFF 
position. Measure resistance between the APP1, APP2 and APP3 circuits at APP harness connector and 
battery ground. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair 
short circuit. 

9) Check APP Sensor Signals For Short To Each Other In Harness 
 
For DTCs P2104, P2121, P2126 and P2131, perform only APP1 to APP2 check, and APP1 to APP3 
check, and for DTC P2104, perform only APP2 to APP3 check. Disconnect PCM and APP sensor harness 
connectors. Measure resistances between the APP1 and APP2 circuits at the APP sensor harness 
connector. Measure resistances between the APP1 and APP3 circuits at the APP sensor harness 
connector. Measure resistances between the APP2 and APP3 circuits at the APP sensor harness 
connector. Are the resistances greater than 10 k/ohms? If yes, go to next step. If no, isolate and repair 
short circuit. 

10) Check APP Sensor For Proper Resistance Through Sensor 
 
Disconnect PCM and APP sensor harness connectors. Measure resistances between ETC REF and ETC 
RTN circuits through the APP sensor, with the accelerator pedal in the "up" position. Measure resistances 
between the APP1 and ETC RTN circuits though the APP sensor. Measure resistances between the APP2 
and ETC RTN circuits though the APP sensor. Measure resistances between the APP3 and ETC RTN 
circuits though the APP sensor. Are the resistances within the table ranges? See APP SENSOR 
CIRCUIT RESISTANCES table. If yes, go to next step. If no, replace APP sensor. If DTC returns, go 
to appropriate test step and repair. If fault repairs do not fix symptom or DTC, go to next step. 

APP SENSOR CIRCUIT RESISTANCES 

 

2003 Ford Pickup F150 

2003 ENGINE PERFORMANCE Self-Diagnostics - CNG, Flex-Fuel & Gasoline