P1484

P1484-CATALYST OVERHEAT DETECTION

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The After treatment Diesel Oxidation Catalyst is designed to react with hydrocarbons in the exhaust stream, this reaction produces heat. The heat can become excessive if too much hydrocarbon enters the After treatment Diesel Oxidation Catalyst too quickly. Excessive heat can damage the diesel after treatment components, so the temperature of the after treatment system is closely monitored by the Powertrain Control Module (PCM). The Exhaust Temperature Sensors are used by the PCM to monitor the temperatures throughout the after treatment system. The Exhaust Temperature Sensors are thermistors and change resistance based on the temperature being measured. The PCM provides a calibrated reference voltage to the sensor. The PCM monitors the voltage on the signal pin and converts this to a temperature value. When the exhaust gas temperature is cold, the sensor or thermistor resistance is high. The PCM signal voltage only pulls down a small amount through the sensor to ground. Therefore, the PCM senses a high signal voltage or low temperature. When the exhaust gas temperature is hot, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the PCM senses a low signal voltage, or a high temperature. The PCM will illuminate the MIL lamp immediately when the diagnostic runs and fails. The PCM will also disable active regeneration of the after treatment diesel particulate filter. This DTC will not self clear and must be cleared by a scan tool.

- When Monitored:
Ignition on.

- Set Condition:
The Powertrain Control Module (PCM) detects that the Exhaust Temperature Sensor 1/1 temperature is greater than calibrated temperature for longer than a calibrated time.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. CHECK THE EXHAUST TEMPERATURE SENSORS
1. Turn the ignition off for five minutes to allow the Exhaust Temperature Sensors to stabilize.
2. Turn the ignition on, engine not running.
3. With the scan tool check the temperature values of the Exhaust Temperature Sensors.

Are the Exhaust Temperature Sensors reading within 6°C (43°F) of each other?

Yes

- Go To 2

No

- Replace the Exhaust Temperature Sensor that is out of range as compared to the others.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

2. CHECK FOR EXCESSIVE ENGINE OIL BEING INTRODUCED INTO THE AFTERTREATMENT SYSTEM
1. Remove the turbocharger outlet and inspect for signs of oil, fuel or moisture being introduced into the After treatment system from the engine.

Was engine oil, fuel or moisture found in the turbocharger exhaust outlet?

Yes

- Locate the cause of possible diesel fuel or engine oil being carried from the engine into the Exhaust system. Inspect the Exhaust for possible damage.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK ENGINE/FUEL SYSTEM PERFORMANCE
1. Perform the CHECKING ENGINE MISFIRE / RUNS ROUGH / PERFORMANCE TEST diagnostic procedure. Checking Engine Misfire / Runs Rough / Performance Test

Were any problems found?

Yes

- Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test