A new diesel engine is available for 2007 (fig. 1). It’s the Duramax 6.6L (RPO LMM). This engine is being released to conform with 2007 US EPA diesel emission regulations, which require a 60% reduction of NOx and a 90% reduction of particulate matter.

This new engine has been designed to be the most powerful and cleanest Duramax Diesel ever offered in the Chevrolet (Silverado, Express, Kodiak) and the GMC (Sierra, Savanna, Top Kick) models.

A number of design strategies have been put in place to meet these new emission regulations. These include both software and hardware:

- Exhaust particulate filter

- Intake air valve

- Revised EGR

- Exhaust tailpipe cooler

- ECM calibration

- Revised injector nozzle flow

- More robust internal engine components and a more efficient turbocharger

EMISSION CONTROL COMPONENT HIGHLIGHTS (fig. 2)

A Diesel Oxidation Catalyst (DOC)

B Exhaust Particulate Filter (DPF)

Diesel Oxidation Catalyst (DOC) -- Reduces hydrocarbons (HC) and oxides of nitrogen (NOx), carbon monoxide (CO) and odor-causing compounds. It also turns the majority of emissions into water and oxygen.

Exhaust Particulate Filter (DPF) -- Traps the particulate matter (solid particles that appear as black smoke) from the engine exhaust before they can be emitted into the atmosphere.

During the regeneration process (explained later), the DOC is heated above its normal operating temperature by a different engine calibration strategy that includes additional fuel injection pulses. The extra heat created by the DOC is used to increase the temperature of the exhaust particulate filter (DPF). The DOC helps obtain and sustain the required temperatures during regeneration.

EXHAUST PARTICULATE FILTER (DPF) OPERATION

The DPF is installed in the exhaust system behind the catalytic converter, and its appearance resembles the catalytic converter. The filter element (fig. 3) is made of porous, catalytically coated silicon carbide, which allows the exhaust gases to pass through, while trapping the solid matter from the exhaust. This decreases particulate matter (soot) and eliminates exhaust smoke. The DPF collects particulates while the engine is running.

To prevent clogging, particulate matter is periodically burned off, leaving ash and yielding carbon dioxide and water. This process is called particulate filter regeneration.

DPF REGENERATION CONTROL (fig. 4)

A Pressure sensor

B Exhaust differential pressure sensor

C Temperature sensor

D Particulate filter

The ECM keeps track of operating conditions to determine the amount of particulate accumulation, and periodically initiates a regeneration process.

Pressure Sensors -- The exhaust differential pressure sensor (EPS) measures the pressure difference between the inlet and outlet of the DPF filter. When the pressure difference has increased above a calibrated threshold, it indicates a high particulate loading condition. The ECM then commands a regeneration event in order to restore the DPF.

The exhaust pressure differential sensor is also used to monitor the filter for cracks or holes in the filter substrate.

Exhaust Gas Temperature Sensors -- During regeneration, two temperature sensors are used to monitor the process. One sensor, located ahead of the DPF, measures the temperature of the exhaust gases leaving the Diesel Oxydizing Catalyst and entering the DPF. This temperature measurement is used by the ECM to control fuel injector flow that is used to maintain temperatures necessary for regeneration. A second temperature sensor, located after the DPF, helps the ECM monitor and regulate the regeneration temperatures and helps protect the system.

DPF REGENERATION OPERATION

Regeneration may occur under several circumstances, called Active Regeneration, Passive Regeneration and Service Regeneration.

Active Regeneration

The regeneration operation is controlled by the ECM, which keeps track of the mileage driven, the amount of fuel consumed, the hours of operation and the exhaust differential pressure.

When the conditions are met for regeneration to occur, the ECM enters a different engine calibration strategy that includes additional fuel injection pulses. This heats the DOC is above its normal operating temperature and regeneration begins.

For the process to complete satisfactorily, the vehicle must be operated continuously for approximately 18 minutes at speeds greater than 30 mph (50 km/h) to efficiently clean the filter. If the engine is allowed to return to idle during this time, the idle speed may be elevated slightly and the operating sound may be different. This is normal, and the driver doesn’t need to do anything different.

During regeneration, the exhaust temperature increases (greater than 500° C), which converts the particulates into harmless gases and ash. The DPF is then clean and ready to filter particulates again.

Driver Notification -- If normal driving does not provide the necessary conditions for regeneration to occur, the pressure differential continues to increase across the exhaust filter. The ECM will illuminate a CLEAN EXHAUST FILTER message on the instrument panel Driver Information Center (C/K only).

When this occurs, the owner manual and a label placed by the driver’s sun visor instruct the customer to drive the vehicle under the conditions necessary for a regeneration to take place until the CLEAN EXHAUST FILTER message no longer appears on the DIC.

Reduced Power -- However, if the CLEAN EXHAUST FILTER message is ignored, the ECM will eventually illuminate the MIL and the Reduced Power lamp. The engine enters the Reduced Power mode, which will require the vehicle to be serviced.

Passive Regeneration

Passive regeneration occurs when exhaust gas temperature is elevated above 300°C
(575° F). These temperatures may be reached when the engine is under heavy load.

Service Regeneration

Service regeneration is performed with the Tech 2, and is used to clean a soot loaded filter during a dealership service visit.

DEALING WITH REGENERATION TEMPERATURES

The exhaust system has been designed to deal with the temperatures involved in the regeneration process. On long wheelbase models, for instance, a heat shield protects the rear axle shock absorbers. All models have an exhaust cooler at the end of the tailpipe
(fig. 5). A vacuum created by the exhaust passing through the openings draws in cool air, which mixes with the exhaust gases. Cooled exhaust exits the tailpipe.

A Exhaust cooler

B Exhaust flow

C Air flow

D Cooled exhaust

IMPORTANT -- There are times when a DPF service regeneration must be performed at the dealership. THIS MUST BE CONDUCTED OUTDOORS. The shop exhaust system will not handle the heat.

DIESEL FUEL AND OIL REQUIREMENTS

The LMM diesel engine requires ultra low sulfur fuel, which limits sulfur content to 15 ppm (parts per million). It also requires use of oil which conforms to the CJ-4 standard established by the American Petroleum Institute (API). This oil offers lower oil consumption and reduces limits for phosphorus, sulfur and ash. Low ash oil is needed to extend the life of the Engine Particulate Filter, as well as to reduce the formation of engine sludge and deposits.

IMPORTANT

Use Ultra Low Sulfur Diesel Fuel (ULSF) only (fig. 6). The emission control hardware may be damaged if high sulfur level fuels are used.

Do not use Low Sulfur Diesel Fuel.

Do not use Off Road Diesel Fuel.

Use only engine oil that has the API classification of CJ-4, which is formulated to work properly with the Diesel Particulate Filter.

Vehicle Modifications -- DO NOT modify any exhaust systems or engine control components, unless it’s GM approved.

- Thanks to Frank Tornambe

For the past two years, the quantity of TechLink newsletters being sent to dealers is 3, 5 or 10 copies, depending on dealership size (US only). During this time, we’ve received numerous inquiries about how dealers can obtain additional copies.

US dealers can order/purchase additional copies of TechLink through the DWD Store. Fill in the total amount desired. You will be billed only for the additional copies.

Dealers can also use the DWD Store to adjust the number of bulletins and other items being received in their weekly DWD box.

TIP: You can also order copies of back issues of TechLink.

IMPORTANT: If a dealer fails to enroll in the subscription process or does not select a specific publication, the default 'ship to' amount is zero (0). In other words, if no selection is made, the dealer will not receive the publication.

Follow this path on the DealerWorld website:

> Business Administration Tab

> DWD Store

> Subscriptions (in left column) (fig. 7 and 8)

TIP: In order to access this path, the proper profile is required. Contact your dealership’s Partner Security Coordinator (PSC) for assistance.

TIP: The Subscription selection can be accessed only by sites with a BAC code.

- Thanks to Mark Stesney

A video has been developed to help you better understand the operation and basic diagnostics of the 2006-07 Pontiac G6 Convertible top (fig. 10).

TIP: This video was sent in DVD format (12442.10V) to all Pontiac dealers during April 2006.

IMPORTANT: Watch this video before diagnosing or making any repairs to the convertible top.

Follow this path on the GM Common Training website to view the streaming video presentation:

1. Log on as a user

2. Click Service Know-How in the menu on the left

3. Click Service Know-How Videos

4. Click Searchable Streaming Video

5. Click Pontiac G6 Folding Top Operation, Diagnosis and Service

IMPORTANT: For additional information on this issue, please refer to IDL Course Numbers 12442.10V and 10206.13D.

- Thanks to Scott Carpenter

The owner of an Equinox or Torrent may comment about wet carpet in the front passenger area.

The body sealant between the sidebody and cowl may be misplaced, allowing water to pass from the top of the right front strut tower into the cabin.

To check for this leak, apply water at the corner of the strut tower (fig. 12). With the passenger side carpet pulled back, look for water to enter (fig. 13). To repair, apply body sealant at the strut tower to dash panel area.

- Thanks to Angelo Girolamo

General Motors has introduced a new GM Heavy Duty Cooling System Cleaner in the U. S. and Canada.

The old part numbers have been discontinued and GMSPO will supersede any orders with the new part numbers.

The new cleaner is a one-part liquid (fig. 16) and replaces the two-part powdered cooling system cleaner previously offered (fig. 17).

GM Heavy Duty Cooling System Cleaner p/n 88861344 (88861345 in Canada) can be used wherever use of the previous product was indicated.

- Thanks to Jay Dankovich

This information applies to Cadillac Escalade and Escalade ESV, Chevrolet Tahoe and Suburban, GMC Yukon and Yukon Denali models.

The rear wiper arm can be broken in a carwash. Some carwash rollover brushes may displace the rear window wiper arm from the rubber park block. When the rear wiper arm is out of the park block, it can be broken by the brush action.

Replace the rubber park block 15895844 and rear wiper arm 15277756. Perform this repair only on vehicles that exhibit the condition.

- Thanks to Dave Roland

Seat belt endlock may occur during rapid retraction of the seatbelt webbing into the retractor. The seatbelt suddenly stops and allows the web sense mechanism to engage the locking mechanism in the retractor. This is a normal function of the retractor and all GM cars and trucks seatbelt systems on the market today exhibit the endlock phenomenon.

How to Release a Locked Retractor

Grasp the seatbelt webbing and slowly and firmly extract 15 - 25mm (0.6 - 1.0 in) of webbing from the retractor.

Release the seatbelt and allow the webbing to retract slowly into the retractor.

Check to see if the seatbelt is released. If it is not released, repeat these steps twice more.

If the retractor does not release at that point, replace the retractor.

This information has been included in the SI for all applicable GM vehicles.

- Thanks to Joel Ebner

Lock cylinder repair kits are now available from GMSPO for 2007 full size utilities. The kits contain all parts, including tumblers, to make a complete cylinder change with any key code sequence.

The following service kits are available:

- Thanks to Paul Radzwilowicz

This information applies to 2001-07 fullsize pickups and utilities, vans, and medium duty trucks with 6.6 L diesel engine.

The use of sealant GM p/n 97720043 is no longer required for such procedures as:

- fuel injector replacement

- fuel injection fuel feed pipe replacement

- fuel injection fuel rail assembly replacement

- valve rocker arm replacement

The following statement is being removed from all SI procedures that require fuel injector pipe removal:

“After installing the fuel injector pipes, clean the injector pipes and apply sealant GM p/n 97720043, at the fittings to prevent moisture and debris from collecting between the line and fitting.”

- Thanks to Jerry Garfield

This information applies to 2004-07 Chevrolet Express, Kodiak, Silverado, GMC Savanna, Sierra, TopKick with LBZ or LLY 6.6L diesel engine with an oil leak.

During initial inspection, the oil leak may look like it is coming from the right rear of the engine or the right rear side of the flywheel housing cover.

The oil leak may actually be coming from the turbo oil pressure feed line or the turbo oil return pipe at the top of the engine.

1. Complete the normal SI procedure for oil leak diagnosis.

2. Add oil dye to the engine oil and run the engine to circulate the dye.

3. Inspect the oil pressure feed hose fittings and the turbo oil drain pipe connections for leaks.

4. Repair the turbo oil pressure feed hose or drain pipe leaks as needed.

5. If the oil leak is not found at the oil feed hose or turbo drain pipe connections, continue with rear of engine inspections and repairs.

- Thanks to Don Langer

Here are some diagnostic tips that apply to the 2007 Cadillac ESV and EXT with KB6 heated and cooled front seats.

If Neither Heated nor Cooled Air is Coming from Neither the Cushion nor the Seatback
(fig. 18)

Check that the connections to the heated/cooled seat module (passenger side) are fully seated. The smaller 10-way and 16-way connectors should have the blue CPA fully seated. Check that the 12-way connector is fully seated.

A Module

B CPA

C 12-way

D 10-way

E 16 way

If Neither Heated nor Cooled Air is Coming from Either the Cushion or the Seatback

For the cushion (fig. 19) -- Look under the cushion near the rear of the seat to be sure the black 8-way connectors that mate the seat harness to the blower takeout are fully seated. Push the connectors together until a click is heard. Then attempt to disengage the connector without depressing the release lever. If it will not disconnect, a full connection has been attained.

A Black 8-way (cushion)

For the back (fig. 20) -- Remove the back panel from the seat back. Locate the back blower. Inspect the black 8-way connector for disengagement. Attempt to pull apart the mating connectors that go to the blower and seat back harness, without depressing the release lever. If the connector disengages, push the connectors together until a click is heard. Then attempt to disengage the connector without depressing the release lever. If it will not disconnect, a full connection has been attained.

A Black 8-way (back)

- Thanks to Dan Lassen

This information applies to all 2007 and earlier GM passenger cars and trucks, including Saturn, HUMMER H2 and H3 and Saab 9-7X.

When checking a vehicle for wheel alignment, do not rely on specifications installed on the alignment equipment that are provided by the equipment manufacturer.

Each year in early summer, GM Chassis Engineering provides wheel alignment specs for the upcoming model year to equipment manufacturers. They then supply the new model year specifications as an update for their equipment.

Revisions to GM wheel alignment specifications are sometimes necessary and are available only in SI. Vendors may not have the most up-to-date specifications. And, regardless, some dealers do not subscribe to the updates from the equipment manufacturers.

Using incorrect specifications can result in:

- vehicles being adjusted unnecessarily

- vehicles being adjusted to incorrect specifications.

This leads to an inferior repair, customer issues, additional cost to the customer and GM warranty.

Before performing any adjustments to vehicle wheel alignment, verify that the specifications loaded into your wheel aligner is up-to-date by checking against what is in SI.

- Thanks to Ron Erman

Owners of some 2007 Silverado and Sierra pickups may hear a clicking noise when closing the tailgate.

The noise may be caused by the right side snap-in hinge bushing. If this is the case, replace it with p/n 15866337.

TIP: The support cables make some noise during closing as they contact the hem of the tailgate during closing. This is minimal and normal.

- Thanks to Jim Will

On a 2005 Buick Rainier, Chevrolet Trailblazer, GMC Envoy, or Saab 9-7x, the security light may be displayed on the IPC for 3-4 seconds after start up with a U1064 stored in several modules.

This could occur if the vehicle is started while the Tech 2 is connected to the vehicle and monitoring any menu under the Diagnostic Circuit Check. This results in excessive bus traffic.

Remove the Tech 2 from the vehicle and re-evaluate operation of the vehicle with each ignition cycle. If the concern is experienced only with the Tech 2 connected as stated above, disconnect the Tech 2 when starting the vehicle, then reconnect after the vehicle has started to review data in Diagnostic Circuit Check.

- Thanks to Dino Poulos