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Home >> Cadillac >> 2004 >> CTS Base, 3.2 N >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 23 (Engine Controls - 3.6L - Diagnosis (DTC P1551 - P2189)) >> Diagnosis >> DTC P2138 >> Diagnostic Aids

Diagnostic Aids

WARNING: This page is about a different variant/trim than selected.
DTC P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Turn ON the ignition, with the engine OFF.
  2. Perform the following tests:
    • Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times.
    • Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times.
  3. Observe the APP Sensors 1 and 2 parameter with a scan tool.
Does the scan tool display Agree?		 - Go to Step 4  Go to Step 3 
3 Observe the DTC information with a scan tool.
Is DTC P0101, P0122, P0123, P0222, P0223, P2122, P2123, P2127, P2128 also set?		 - Go to Diagnostic Trouble Code (DTC) List Go to Step 5 
4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 5  Go to Diagnostic Aids
5
  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor harness connector.
  3. Turn ON the ignition, with the engine OFF.
    4. IMPORTANT: Use the J 35616-200  Test Lamp Kit for this test. If the J 35616-200  is not available, use a test lamp that measures more than 20 ohms.
  4. Connect a test lamp between the 5-volt reference circuit of the APP sensor 1 and a good ground.
  5. Connect a DMM to the probe of the test lamp and a good ground. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage within the specified range?		 4.8-5.1 V Go to Step 6  Go to Step 11 
6
    IMPORTANT: Use the J 35616-200  Test Lamp Kit for this test. If the J 35616-200  is not available, use a test lamp that measures more than 20 ohms.
  1. Connect a test lamp between the 5-volt reference circuit of the APP sensor 2 and a good ground.
  2. Connect a DMM to the probe of the test lamp and a good ground. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage within the specified range?		 4.8-5.1 V Go to Step 7  Go to Step 11 
7
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the signal circuit of the APP sensor 1.
  2. Observe the APP sensor 1 voltage parameter with a scan tool.
Is the voltage more than the specified value?		 4.8 V Go to Step 8  Go to Step 12 
8
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the signal circuit of the APP sensor 2.
  2. Observe the APP sensor 2 voltage parameter with a scan tool.
Is the voltage more than the specified value?		 4.8 V Go to Step 9  Go to Step 12 
9
  1. Turn OFF the ignition.
  2. Remove the ECM/TCM fuse from the underhood fuse block.
    3. NOTE: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
  3. Measure the resistance from the low reference circuit of the APP sensor 1 to a good ground with a DMM.
Is the resistance less than the specified value?		 10 ohm Go to Step 10  Go to Step 13 
10
NOTE: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
Measure the resistance from the low reference circuit of the APP sensor 2 to a good ground with a DMM.Is the resistance less than the specified value?		 10 ohm Go to Step 14  Go to Step 13 
11
IMPORTANT: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.
Test the 5-volt reference circuit of the APP sensor 1 or 2 for the following:
  • An open
  • A short to ground
  • A short to voltage
  • High resistance
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
12 Test the signal circuit of the APP sensor 1 or 2 for the following:
  • An open
  • A short to ground
  • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
13 Test the low reference circuit of the APP sensor 1 or 2 for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
14 Test the signal circuit of APP sensor 1 for a short to the signal circuit of APP sensor 2. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 15 
15 Test for an intermittent and for a poor connection at the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 17 
16 Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 18 
17 Replace the APP sensor. Refer to Accelerator Pedal Position (APP) Sensor Replacement .
Did you compete the replacement?		 - Go to Step 19  -
18 Replace the engine control module (ECM). Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 19  -
19
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 20 
20 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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