Document ID: 2366350

=20

Subject:

Cleaning Diesel Engine=20 Injectors

Models:

2006-2010 Chevrolet Express, = Kodiak,=20 Silverado

2006-2010 GMC Savana, Sierra,=20 Topkick

Equipped with the 6.6L diesel = engines RPO=20 code LBZ LLY and LMM

The following diagnosis might be helpful if the vehicle exhibits the=20 symptom(s) described in this PI.

Condition/Concern:

A dealer may encounter a customer concern of rough running, P0191, or = a crank=20 no start.

Poor fuel quality may have induced the rough running, P0191, or no = start. A=20 dealer may notice the vehicle has one or more cylinders with the = injector=20 balance rates out of specification, a DTC P0191, or a crank no start. = When=20 diagnosing a crank no start condition it is possible the injector = pintles are=20 stuck closed. A no start with clogged injectors will have sufficient = pressure in=20 the fuel rail when the engine is cranked. Cranking pressure will = normally be=20 around 4000-5000 psi or 27-34 MPA during a no start due to stuck=20 injectors.

Recommendation/Instructions:

If a dealer encounters a vehicle with a rough running (high injector = balance=20 rate), a P0191, or a no start with sufficient pressure in the fuel rail, = cleaning injectors may alleviate the condition.

Injector cleanings are only suggested when the dealer has found fuel=20 contamination or suspects fuel contamination.

Clean injectors if injector balance rates are not within = +4 mm=C2=B3 and=20 -6.9 mm=C2=B3. Cleaning the injectors may free up a sticking pintle or = clean the=20 residue left by poor fuel.=20
Clean injectors if the engine is a no start, and the = vehicle has=20 sufficient pressure in the fuel rail to start. Cranking fuel rail = pressure=20 when all 8 injectors are clogged is approximately 4000-5000 psi or = 27-34 MPA.=20
Clean injectors if P0191 has set due to a slow fuel rail = pressure=20 (FRP) decay rate. P0191 may set due to an accumulated but harmless = varnish=20 build-up on the fuel injectors. If servicing a 2006-2008 model year = vehicle=20 please see the newest version of bulletin 09-06-04-022 for P0191 ECM=20 calibration information.

Injector Cleaning Procedure:

To clean the injectors the dealer will be using a mixture of GM Upper = Engine=20 Fuel Injector Cleaner p/n 88861802 (88861804 in Canada) and diesel fuel. = The=20 cleaner will be connected at the rear of engine fuel line quick = disconnects. Use=20 an approved one gallon diesel fuel can for this process. Two fuel lines=20 (approved for use with diesel fuel) will also be needed. Remove the = quick=20 disconnects at the rear of the engine. Install the two rubber fuel lines = in the=20 place of the fuel suction and return lines. Make sure these hoses are = long=20 enough to reach the fuel can sitting safely on the floor next to the = vehicle.=20 Use 1/2 gallon of fresh clean number 2 diesel fuel (no bio-diesel) and = 13 ounces=20 of GM Upper Engine Fuel Injector Cleaner to complete this process.

Run the engine until the complete mixture has been cycled through the = engine.

With a no start condition, try to start the engine multiple times = until the=20 mixture starts to flow through the system. Make sure not to overheat the = starter=20 during this process. Let the starter cool down between each = engagement.

Note: If a heavy concentration of = debris or=20 contaminates quickly fills the fuel can (from the return side of the = fuel=20 system) do not continue to cycle it through the system. Any contaminated = fuel=20 removed from the vehicle will need to be disposed of following city = and/or state=20 guidelines.

Evaluate the customer concern after the injector cleaning process has = been=20 completed.

Please follow this diagnostic or repair process thoroughly and = complete each=20 step. If the condition exhibited is resolved without completing every = step, the=20 remaining steps do not need to be performed.

GM bulletins are intended for use by = professional=20 technicians, NOT a "do-it-yourselfer". They are written to = inform=20 these technicians of conditions that may occur on some vehicles, = or to=20 provide information that could assist in the proper service of a=20 vehicle. Properly trained technicians have the equipment, = tools,=20 safety instructions, and know-how to do a job properly and = safely. =20 If a condition is described, DO NOT assume that the bulletin = applies to=20 your vehicle, or that your vehicle will have that condition. = See=20 your GM dealer for information on whether your vehicle may benefit = from=20 the information.

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=C2=A9 2009 General Motors. All rights = reserved.=20