Section 91.1
SPN 2629/FMI 3

This condition is typically open circuit or short to power.‪

Section 91.1.1
Open Circuit/Short to Power Check

Check as follows:‪

1. Turn the ignition ON (key ON, engine OFF).
2. Check for multiple codes.
   1. If codes 1636/3, 2629/3 and 412/3 are active at the same time, go to step 3 .
   2. If only fault 2629/3 is active, go to step 5 .
3. Disconnect the Intake Air Temperature Sensor.
4. Measure the voltage between pin 1 of the Intake Air Temperature Sensor and ground.
   1. If the voltage is greater than 2.75 volts, repair the short to power between pin 52 of the MCM 120–pin connector and the Intake Air Temperature Sensor, the Turbo Compressor Out Temperature Sensor (TCO Sensor) and the EGR Temperature Sensor. Refer to "91.1.1.1 Verify Repairs" .
   2. If no voltage is present on pin 1 of the Intake Air Temperature Sensor, repair the open circuit between pin 52 of the MCM 120–pin connector and the Intake Air Temperature Sensor, the Turbo Compressor Out Temperature Sensor and the EGR Temperature Sensor. Refer to "91.1.1.1 Verify Repairs" .
5. Disconnect the TCO Sensor.
6. Measure the resistance across pins 1 and 2 of the TCO Sensor.
   1. If the resistance is not within the range listed in Table "Turbo Compressor Outlet Temperature Sensor Resistance" , replace the TCO Sensor. Refer to "91.1.1.1 Verify Repairs"
   2. If the resistance is within the range listed in Table "Turbo Compressor Outlet Temperature Sensor Resistance" , go to step 7 .

   Temperature (°F)‪	Temperature (°C)‪	Maximum Resistance (KΩ)‪	Minimum Resistance (KΩ)‪
   32‪	0‪	1053.00‪	634.00‪
   50‪	10‪	601.75‪	367.98‪
   68‪	20‪	357.27‪	224.97‪
   86‪	30‪	219.54‪	142.08‪
   104‪	40‪	139.17‪	92.40‪
   122‪	50‪	90.75‪	61.72‪
   140‪	60‪	60.72‪	42.23‪
   158‪	70‪	41.58‪	29.55‪
   176‪	80‪	29.10‪	21.09‪
   194‪	90‪	20.77‪	15.34‪

   Table 1. Turbo Compressor Outlet Temperature Sensor Resistance
7. Turn the ignition ON (key ON, engine OFF).
8. Measure the voltage between pins 1 and 2 of the TCO Sensor harness connector.
   1. If the voltage is between 2.75 and 3.25 volts, refer to "91.1.1.1 Verify Repairs" .
   2. If the voltage is less than 2.75 volts, go to step 9 .
9. Measure the voltage between pin 2 of the TCO Sensor harness connector and ground.
   1. If the voltage is between 2.75 and 3.25 volts, repair the open circuit between pin 1 of the TCO Sensor harness connector and pin 52 of the 120–pin MCM connector. See Figure "Turbo Compressor Outlet Temperature Sensor" . Refer to "91.1.1.1 Verify Repairs" .
   

   Figure 1. Turbo Compressor Outlet Temperature Sensor

   2. If the voltage is less than 2.75 volts, repair the open circuit between pin 2 of the TCO Sensor harness connector and pin 112 of the 120–pin MCM connector. Refer to "91.1.1.1 Verify Repairs" .

Section 91.1.1.1
Verify Repairs

Verify repairs as follows:‪

1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.
4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel Customer Support Center at 313–592–5800.