DDEC III/IV Single ECM Troubleshooting – Section 67.5 Map Input Voltage Low

Section 67.5
Map Input Voltage Low

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

Section 67.5.1
Sensor Check

Perform the following steps to check the sensor.‪

1. Turn vehicle ignition OFF.
2. Disconnect the MAP sensor connector.
3. Install a jumper wire between sockets B and C of the MAP sensor harness connector. See Figure "Manifold Air Pressure Sensor" .
4. Turn ignition ON.
5. Start engine
6. Read active codes.
   1. If active code 106/4 and any other codes are logged, refer to "67.5.3 Check for +5 Volt" .
   2. If active code 106/4 and any other codes except 106/3 are logged, refer to "67.5.2 Check MAP Sensor Connectors" .
   

   Figure 1. Manifold Air Pressure Sensor

Section 67.5.2
Check MAP Sensor Connectors

Perform the following steps to check the MAP sensor connector. ‪

1. Check terminals at the MAP sensor connectors (both the MAP and harness side) for damage: bent, corroded and unseated pins or sockets.
   1. If the terminals and connectors are damaged, repair them. Refer to "67.5.10 Verify Repairs" .
   2. If the terminals and connectors are not damaged, replace the MAP sensor. Refer to "67.5.10 Verify Repairs" .

Section 67.5.3
Check for +5 Volt

Perform the following steps to check for +5 volt.‪

1. Remove jumper.
2. Turn ignition ON.
3. Measure voltage on MAP sensor harness connector, pin B (red lead) to pin A (black lead).
   1. If the voltage measurement is greater than 6 volts, refer to "67.5.9 Check for Short to Battery +" .
   2. If the voltage measurement is between 4 and 6 volts, refer to "67.5.4 Check for Signal Open" .
   3. If the voltage measurement is less than 4 volts, refer to "67.5.7 Check for Open +5 Volt Line" .

Section 67.5.4
Check for Signal Open

Perform the following steps to check for signal open.‪

1. Turn vehicle ignition OFF.
2. Disconnect the engine harness connector at the ECM.
3. Install a jumper wire between pins A and C of the MAP sensor harness connector. See Figure "Manifold Air Pressure Sensor " .
4. Measure resistance between sockets P1 and Y2 on the engine harness connector.
   1. If the resistance measurement is less than or equal to 5 Ω, refer to "67.5.5 Check for Short" .
   2. If the resistance measurement is greater than 5 Ω, or open, the signal line (#432) is open; repair the open. Refer to "67.5.10 Verify Repairs" .
   

   Figure 2. Manifold Air Pressure Sensor

Section 67.5.5
Check for Short

Perform the following steps to check for short.‪

1. Remove jumper.
2. Measure resistance between pins A and C on the MAP sensor harness connector.
   1. If measured resistance between pins A and C is greater than 100 Ω, or open, go to step 3
   2. If measured resistance between pins A and C is less than 100 Ω, the signal line (#432) is shorted to the return line (#452). Repair the short. Refer to "67.5.10 Verify Repairs" .
3. Also measure resistance between socket C and a good ground.
   1. If measured resistance between socket C and a good ground is greater than 100 Ω, or open, refer to "67.5.6 Check ECM Connectors" .
   2. If measured resistance between socket C and a good ground is less than 100 Ω, the signal line (#432) is shorted to the battery ground. Repair the short and refer to "67.5.10 Verify Repairs" .

Section 67.5.6
Check ECM Connectors

Perform the following steps to check the ECM connectors.‪

1. Check terminals at the ECM harness connector (both ECM and harness side) for damage: bent, corroded, and unseated pins or sockets. See Figure "Engine Harness Connector to Manifold Air Pressure Sensor " .
   1. If terminals and connectors are damaged, repair them and refer to "67.5.10 Verify Repairs" .
   2. If terminals and connectors are not damaged, install a test ECM. Refer to "67.5.10 Verify Repairs" .
   

   Figure 3. Engine Harness Connector to Manifold Air Pressure Sensor

Section 67.5.7
Check for Open +5 Volt Line

Perform the following steps to check for open +5 volt line.‪

1. Turn vehicle ignition OFF.
2. Disconnect the engine harness connectors at the ECM.
3. Install a jumper wire between pins A and B of the MAP sensor harness connector. See Figure "5-Way ECM Power Connector" .
4. Read resistance between sockets W1 and Y2 on the engine harness connector.
   1. If the resistance measurement is less than or equal to 5 Ω, refer to "67.5.8 Check for Short" .
   2. If the resistance measurement is greater than 5 Ω, or open, the vehicle +5 volt line (#416) is open. Repair open. Refer to "67.5.10 Verify Repairs" .
   

   Figure 4. 5-Way ECM Power Connector

Section 67.5.8
Check for Short

Perform the following steps to check for short.‪

1. Remove jumper.
2. Measure resistance between pins A and B on the MAP sensor harness connector. See Figure "Manifold Air Pressure Sensor " .
   1. If measured resistance between pins A and B is greater than 100 Ω, or open, go to step 3
   2. If measured resistance between pins A and B is less than 100 Ω, the 5 volt supply (#416) is shorted to the return line (#452). Repair the short. Refer to "67.5.10 Verify Repairs" .
3. Also measure resistance between socket B and a good ground.
   1. If measured resistance between socket B and a good ground is greater than 100 Ω, or open, refer to "67.5.6 Check ECM Connectors" .
   2. If measured resistance between socket B and a good ground is less than 100 Ω, the 5 volt supply (#416) is shorted to the battery ground. Repair the short and refer to "67.5.10 Verify Repairs" .
   

   Figure 5. Manifold Air Pressure Sensor

Section 67.5.9
Check for Short to Battery +

Perform the following steps to check for short to battery +.‪

1. Turn vehicle ignition OFF.
2. Remove both fuses to the ECM.
3. Disconnect the engine harness, vehicle harness, and 5-way power connectors at the ECM.
4. Measure resistance between socket W1 on the engine harness connector and socket B3 of the vehicle harness connector, and between W1 and the 5-way power harness sockets A and C. See Figure "ECM Vehicle Harness Connector" .
   1. If measured resistance is less than or equal to 100 Ω, a short exists between sockets where less than 100 Ω was measured. Repair short and reinsert fuses. Refer to "67.5.10 Verify Repairs" .
   2. If the resistance measurement is greater than 100 Ω, or open, refer to "67.5.6 Check ECM Connectors" .
   

   Figure 6. ECM Vehicle Harness Connector

Section 67.5.10
Verify Repairs

Perform the following steps to verify repairs.‪

1. Turn vehicle ignition 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, no further troubleshooting is required.
   2. If code 106/4 and any other codes are logged, all system diagnostics are complete. Please review this section from the first step to find the error. Refer to "67.5.1 Sensor Check" .
   3. If code 106/4 is not logged and any other codes are logged, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .