91.1 SPN 2629/FMI 3
This condition is typically open circuit or short to power.
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.
[a] If codes 1636/3, 2629/3 and 412/3 are active at the same time, go to step 3.
[b] 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.
[a] 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 section 91.1.1.1.
[b] 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 section 91.1.1.1.
5. Disconnect the TCO Sensor.
6. Measure the resistance across pins 1 and 2 of the TCO Sensor.
[a] If the resistance is not within the range listed in Table 91-1, replace the TCO Sensor.
Refer to section 91.1.1.1
[b] If the resistance is within the range listed in Table 91-1, go to step 7.
7. Turn the ignition ON (key ON, engine OFF).
8. Measure the voltage between pins 1 and 2 of the TCO Sensor harness connector.
[a] If the voltage is between 2.75 and 3.25 volts, refer to section 91.1.1.1.
[b] 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.
[a] 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 91-1. Refer to section 91.1.1.1.
[b]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 section 91.1.1.1.
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.
