DDEC III/IV Single ECM Troubleshooting – Section 67.4 Map Input Voltage High

Section 67.4
Map Input Voltage High

Follow these steps to troubleshoot manifold air pressure (MAP) input voltage high. ‪

Section 67.4.1
Sensor Check

Perform the following steps to check the sensor.‪

1. Turn vehicle ignition OFF.
2. Disconnect the MAP sensor connector. See Figure "Manifold Air Pressure Sensor" .
3. Start and run the engine at idle.
4. Read active codes logged.
   1. If active code 106/3 and any other codes are logged, refer to "67.4.4 Check for Short to +5 Volt Line" .
   2. If active code 106/4 and any other codes except 106/3 are logged, refer to "67.4.3 Check MAP Sensor Connectors" .
   

   Figure 1. Manifold Air Pressure Sensor

Section 67.4.2
Return Circuit Check

Perform the following steps to check the return circuit.‪

1. Turn ignition switch OFF.
2. Install a jumper wire between pin A and pin C of the MAP sensor harness connector. See Figure "Manifold Air Pressure Sensor" .
3. Disconnect the engine harness connector at the ECM. See Figure "ECM Engine Harness Connector" .
4. Measure resistance between sockets P1 and Y2 on the engine harness connector.
   1. If resistance measurement is less than or equal to 5 Ω, refer to "67.4.3 Check MAP Sensor Connectors" .
   2. If resistance measurement is greater than 5 Ω, the return line #452 is open. Repair the open. Refer to "67.4.7 Verify Repairs" .
   

   Figure 2. Manifold Air Pressure Sensor

   

   Figure 3. ECM Engine Harness Connector

Section 67.4.3
Check MAP Sensor Connectors

Perform the following steps to check the MAP sensor connectors. ‪

1. Check terminals at the MAP sensor connector (both sensor and harness side) for damage: bent, corroded, and unseated pins or sockets. See Figure "Manifold Air Pressure Sensor" .
   1. If the terminals and connectors are damaged, repair them. Refer to "67.4.7 Verify Repairs" .
   2. If the terminals and connectors are not damaged, replace the MAP sensor. Refer to "67.4.7 Verify Repairs" .
   

   Figure 4. Manifold Air Pressure Sensor

Section 67.4.4
Check for Short to +5 Volt Line

Perform the following steps to check for a short to the +5 volt line:‪

1. Turn vehicle ignition OFF.
2. Disconnect engine harness connector from the ECM.
3. Measure resistance between sockets P1 and W1 on the engine harness connector. See Figure "ECM Engine Harness Connector" .
   1. If measured resistance is less than or equal to 10,000 Ω, the signal line #432 is shorted to the engine +5 volt line #416. Repair short. Refer to "67.4.7 Verify Repairs" .
   2. If measured resistance is greater than 10,000 Ω, or open, refer to "67.4.5 Check for Short to Battery" .
   

   Figure 5. ECM Engine Harness Connector

Section 67.4.5
Check for Short to Battery

Perform the following steps to check for a short to the battery (+):‪

1. Remove both fuses to the ECM.
2. Disconnect the vehicle harness and 5-way power connector harness at the ECM. See Figure "5-Way ECM Power Connector" .
3. Measure resistance between sockets P1 of the engine harness connector and B3 on the vehicle harness connector.
4. Measure resistance between socket P1 on the engine harness connector and the 5-way power harness connector sockets A and C.
   1. If the resistance measurement is less than or equal to 100 Ω, a short exists between sockets where the measurement was taken. Repair short and reinsert fuses, or reset breakers. Refer to "67.4.7 Verify Repairs" .
   2. If the resistance measurement is greater than 100 Ω, or open, refer to "67.4.6 Check ECM Connectors" .
   

   Figure 6. 5-Way ECM Power Connector

Section 67.4.6
Check ECM Connectors

Perform the following steps to check the ECM connectors.‪

1. Check terminals at the ECM engine harness connector (both the ECM and harness side) for damage: bent, corroded, and unseated pins or sockets.
   1. If terminals and connectors are damaged, repair both. Refer to "67.4.7 Verify Repairs" .
   2. If terminals and connectors are not damaged, reprogram the ECM. Refer to "67.4.7 Verify Repairs" .

Section 67.4.7
Verify Repairs

Perform the following steps to verify repairs.‪

1. Turn ignition switch OFF.
2. Reconnect all connectors.
3. Turn ignition ON.
4. Clear codes.
5. Start and run the engine for one minute.
6. Stop engine.
7. Check DDR for codes.
   1. If no codes are logged, troubleshooting is complete.
   2. If code 106/3 is not logged, and other codes are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .
   3. If code 106/3 is logged, and other codes are logged, refer to "67.4.1 Sensor Check" .