On the 2010-2011 Express and Savana and 2011 Silverado and Sierra equipped with the 6.6L Duramax Diesel engine (RPO LML, LGH), the Diesel Exhaust Fluid (DEF) may freeze if the vehicle is operated in low ambient temperatures (16°F, -9°C or below) for extended periods of time.
As a result, the vehicle may be speed limited and the following Driver Information Center (DIC) messages may be displayed: Exhaust Fluid Low, Exhaust Fluid Empty - Refill Now, or Exhaust Fluid Range: XXX (range shown depends on message level). These conditions may be present even if the ambient temperatures are not currently less than 20°F (X°C), but were previously.
TIP: All engine DTCs must be repaired before the DEF messages are addressed, including DTCs concerning poor quality DEF and servicing the DEF system.
For low DEF messages and speed limiting on a vehicle known to have a full tank of DEF, an updated calibration is available in TIS2Web. Refer to #PIP4864D for additional information.
DEF Level
The DEF system includes three reductant (DEF) heaters, which are located in the reductant reservoir, the supply line to the reductant injector, and at the reductant pump. The ECM monitors the reductant temperature sensor in the reservoir in order to determine if reductant temperature is below its freeze point. If the ECM determines that the reductant may be frozen, it signals the Glow Plug Control Module (GPCM) to energize the reductant heaters. DEF will not be damaged by freezing, and will remain fully usable when thawed.
When the DEF is frozen, the DEF level may not be recognized until the fluid around the Discrete Level Sensors (DLS) has thawed.
To verify if the fluid is frozen, use the Tech 2 DEF level reading function. After a normal DEF tank fill, the DEF level reading on the Tech 2 should increase to 100%. If fluid was added and the level does not change, the fluid may be frozen. The fluid will have to be thawed before completing any repairs. A reading of 100% does not indicate that the entire tank is thawed. As the fluid in the tank is thawing, it is normal to see the level sensors in the tank react differently than when the fluid is thawed.
If the fluid is determined to be frozen, the truck may be in "Frozen Tank Status," in which the level sensors cannot determine the fluid level in the tank and the ECM assumes a default fluid level and bases remaining range on DEF dosing history. This may result in a Fluid Low or Fluid Empty message being displayed.
The updated calibration in #PIP4864D will allow the ECM to check the level of DEF when a range of less than 1,000 miles (1,609 km) occurs; previously, DEF level was checked when the ranged dropped below 300 miles (483 km). Also, the DEF level will be checked when the temperature has warmed enough to have thawed the fluid. These conditions will be intermittent based on ambient temperature changes.
Programming
It is critical to follow the information as outlined in #PIP4864D. Here are some of the highlights.
Before programming to address the DEF messages, drain the DEF tank. Verify the tank is completely empty by using the Tech 2 to check that all three Reductant Level Sensors are inactive.
The ECM is reprogrammed using a two-part level reset calibration. Part one of the calibration is titled: ECM DEF tank fluid level warning latched reset programming per PIP4864.
After programming part one of the calibration, fill the DEF tank with a maximum of 5 gallons (18.9 L). Do not add DEF while the ignition is ON or while the vehicle is running. Use the Tech 2 to verify that the Reductant Level Remaining Distance has reset to more than 4,000 miles (6,430 km). This verifies that the calibration was installed correctly.
Part two of the calibration is titled: Engine Control Module. If this calibration is not programmed, the vehicle will be limited to 5 mph (9 km/h).
TIP: Refer for # PIP4864D for complete details about the programming procedures. Every step must be performed as detailed in order to properly complete the repair.
Do not replace the DEF tank or other DEF system components for this condition unless Service Information diagnostics indicate the need.
