Page 817 of 5267
18.SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS
Measure the resistance between the APPS 2 supply circuit at the ECM
connector and all other circuits in the ECM connector.
Is the resistance greater than 100 K ohms?
Ye s>>
Go To 19
No>>
Repair the supply circuit shorted to other circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
19.RETURN CIRCUIT OPEN
Measure the resistance on the APPS 2 return circuit between the sen-
sor connector and the ECM connector.
Is the resistance less than 10 ohms?
Ye s>>
Go To 20
No>>
Repair the open return circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 818 of 5267
20.SIGANAL CIRCUIT SHORTED TO SUPPLY CIRCUIT
Measure the resistance between the APPS 2 signal circuit in the sensor
connector and the PPS 2 supply circuit in the sensor connector.
Is the resistance greater than 100 K ohms?
Ye s>>
Go To 21
No>>
Repair the signal circuit shorted to the supply.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
21.RETURN CIRCUIT SHORTED TO OTHER CIRCUITS
Measure the resistance between the APPS 2 return circuit at the ECM
connector and all other circuits in the ECM connector.
Ye s>>
Go To 22
No>>
Repair the return circuit shorted to other circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 819 of 5267

22.ECM
Reconnect the ECM connectors.
Reconnect the APPS connector.
Turn Ignition on, engine off.
While monitoring with the scan tool, disconnect the sensor connector.
Did a APPS 1 and APPS 2 voltage too low DTC set?
Ye s>>
Go To 23
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
23.APPS
Reconnect the APPS connector.
Monitor the APPS 1 and APPS 2 voltage with the scan tool while depressing theacceralator pedal.
Is the voltage transition shown on the scan tool smooth while depressing the acceraaltor and is the
voltage from APPS 1 twice as much as the voltage from APPS 2?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No>>
Replace the APPS.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 820 of 5267
P2122-PPS 1 VOLTAGE TOO LOW
For a complete wiring diagramRefer to Section 8W.
Page 821 of 5267

When Monitored:
While the key is on and during engine operation.
Set Condition:
The APPS circuit voltage at the ECM goes below 0.13 volt for more than 2 seconds.
Possible Causes
APPS
ECM
(K23) APPS NO. 1 SIGNAL CIRCUIT OPEN
(F855) APPS NO. 1 5-VOLT SUPPLY OPEN
(K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO GROUND
(K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
(F855) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(F855) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.(K23) APPS NO. 1 SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the APPS harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance of the (K23) APPS No. 1 signal circuit between
the APPS sensor harness connector and the ECMharness connector.
Is the resistance less than 10 ohms?
Ye s>>
Go To 2
No>>
Repair the (K23) APPS No. 1 signal circuit open.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 822 of 5267
2.(F855) APPS NO. 1 5-VOLT SUPPLY OPEN
Measure the resistance of the (F855) APPS No. 1 5-volt supply circuit
between the APPS sensor harness connector and the ECM harness
connector.
Is the resistance less than 10 ohms?
Ye s>>
Go To 3
No>>
Repair the (F855) APPS No. 1 5-volt supply open.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
3.(K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between the (K23) APPS No. 1 signal circuit at
the sensor harness connector and battery negative.
Is the resistance greater than 100 k ohms?
Ye s>>
Go To 4
No>>
Repair the (K23) APPS No. 1 signal circuit shorted to
ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 823 of 5267
4.(K23) APPS NO. 1 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
Measure the resistance between the (K23) APPS No. 1 signal circuit at
the sensor harness connector and all other circuits in the ECM harness
connector.
Is the resistance greater than 100 k ohms?
Ye s>>
Go To 5
No>>
Repair the (K23) APPS No. 1 signal circuit shorted to other
circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
5.(F855) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Measure the resistance between the (F855) APPS No. 1 5-volt supply
circuit at the sensor harness connector and battery negative.
Is the resistance greater than 100 k ohms?
Ye s>>
Go To 6
No>>
Repair the (F855) APPS No. 1 5-volt supply circuit shorted
to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 824 of 5267

6.(F855) APPS NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS
Measure the resistance between the (F855) APPS No. 1 5-volt supply
circuit at the sensor harness connector and all other circuits in the ECM
harness connector.
Is the resistance greater than 100 k ohms?
Ye s>>
Go To 7
No>>
Repair the (F855) APPS No. 1 5-volt supply circuit shorted
to other circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
7.ECM
Reconnect the ECM harness connectors.
Turn the ignition on.
While monitoring with the scan tool, connect a jumper wire between the (K23) APPS No. 1 signal circuit at the
sensor harness connector and the (F855) APPS No. 1 5-volt supply circuit atthe sensor harness connector.
NOTE: With the sensor disconnected it is normal to have a APPS 1 and APPS 2 lowvoltage DTC set.
Did DTC P2123 set?
Ye s>>
Go To 8
No>>
Replace and program the ECM in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
8.APPS
Reconnect the APPS harness connector.
Monitor the APPS 1 and APPS 2 voltage with the scan tool while depressing thethrottle pedal.
Is the voltage transition shown on the scan tool smooth while depressing thethrottleandisthevolta
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No>>
Replace the APPS.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)