Chevrolet Silverado / GMC Sierra. Service manual — part 1791

If the vehicle is equipped with a 6.6 L diesel engine do not perform this diagnostic. The exhaust
system does not have a location for installing the J 35314-A Exhaust Back Pressure Gage. See
Special Tools. Instead remove the suspect component, operate the vehicle, verify for improved
performance. If performance is improved then replace the faulty component.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

4: The exhaust system has very low back pressure under normal conditions. If the exhaust
system is restricted, a significant increase in the exhaust pressure is noticed on the J 35314-
A . See Special Tools. Removing the heated oxygen sensor (HO2S) sensor may set a DTC.
When finishing this diagnostic table, be sure to clear all codes.

5: This step will isolate the catalytic converter from the remainder of the exhaust system.

8: Confirming that the condition has been fixed is essential. If the symptom still exists and
the vehicle has a dual exhaust system, proceed to Step 2 and repeat diagnostic procedure on
the opposite exhaust pipe.

Restricted Exhaust

CAUTION: While engine is operating, the exhaust system will become

extremely hot. To prevent burns avoid contacting a hot
exhaust system.

IMPORTANT: Do not replace a restricted particulate filter. Repair the engine

condition that clogged the particulate filter, and then attempt to
perform a service regeneration. Refer to Exhaust Particulate
Filter Cleaning (LMM DPF Regeneration Enable) or Exhaust
Particulate Filter Cleaning (LMM DPF Service Regeneration).

Step

Action

Value(s)

Yes

No

1

Did you verify the customers complaint?

-

Go to Step 2

-

2

Did you review the exhaust symptoms
diagnostic information and perform the
necessary inspections?

-

Go to Step 3

Go to
Symptoms -
Engine
Exhaust

3

Is the vehicle equipped with a 6.6L diesel
engine?

-

Go to
Diagnostic
Aids

Go to Step 4

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Exhaust - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

4

1. Remove the HO2S that is in front of

and closest to the catalytic converter.
Refer to Heated Oxygen Sensor
Replacement - Bank 1 Sensor 1 or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 1 for
the 4.3L engine, or to Heated
Oxygen Sensor Replacement -
Bank 1 Sensor 1 (1500 Series) or
Heated Oxygen Sensor
Replacement - Bank 1 Sensor 1
(2500 Series) or Heated Oxygen
Sensor Replacement - Bank 1
Sensor 1 (2500 Series -
Cab/Chassis) or Heated Oxygen
Sensor Replacement - Bank 2
Sensor 1 (1500 Series) or Heated
Oxygen Sensor Replacement -
Bank 2 Sensor 1 (2500 Series) or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 1
(2500 Series - Cab/Chassis) for the
4.8L, 5.3L, 6.0L, and 6.2L engines.

2. Install the J 35314-A Exhaust Back

Pressure Gage in place of the HO2S.
See Special Tools.

3. Start the engine.

4. Increase and monitor the engine

speed at 2,000 RPM.

5. Observe the exhaust system back

pressure reading on the gage.

Does the reading exceed the specified
value?

20 kPa (3

psi)

If equipped

with a 4.8L,

5.3L, 6.0L,

or 6.2L - 3.4

kPa (0.5 psi)

Go to Step 5 Go to Step 8

1. Turn the engine off and place the

ignition in the lock position.

2. Remove the J 35314-A . See Special

Tools.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Exhaust - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

5

3. Re-install the HO2S. Refer to

Heated Oxygen Sensor
Replacement - Bank 1 Sensor 1 or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 1 for
the 4.3L engine, or to Heated
Oxygen Sensor Replacement -
Bank 1 Sensor 1 (1500 Series) or
Heated Oxygen Sensor
Replacement - Bank 1 Sensor 1
(2500 Series) or Heated Oxygen
Sensor Replacement - Bank 1
Sensor 1 (2500 Series -
Cab/Chassis) or Heated Oxygen
Sensor Replacement - Bank 2
Sensor 1 (1500 Series) or Heated
Oxygen Sensor Replacement -
Bank 2 Sensor 1 (2500 Series) or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 1
(2500 Series - Cab/Chassis) for the
4.8L, 5.3L, 6.0L, and 6.2L engines.

4. Remove the post-catalyst HO2S.

Refer to Heated Oxygen Sensor
Replacement - Bank 1 Sensor 2 or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 2 for
the 4.3L engine, or to Heated
Oxygen Sensor Replacement -
Bank 1 Sensor 2 (1500 Series) or
Heated Oxygen Sensor
Replacement - Bank 1 Sensor 2
(2500 Series) or Heated Oxygen
Sensor Replacement - Bank 1
Sensor 2 (2500 Series -
Cab/Chassis) or Heated Oxygen
Sensor Replacement - Bank 2
Sensor 2 (1500 Series) or Heated
Oxygen Sensor Replacement -

20 kPa (3

psi)

If equipped

with a 4.8L,

5.3L, 6.0L,

or 6.2L - 3.4

kPa (0.5 psi)

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Exhaust - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Bank 2 Sensor 2 (2500 Series) or
Heated Oxygen Sensor
Replacement - Bank 2 Sensor 2
(2500 Series - Cab/Chassis) for the
4.8L, 5.3L, 6.0L, and 6.2L engines.

5. Install the J 35314-A in place of the

post HO2S. See Special Tools.

6. Start the engine.

7. Increase and monitor the engine

speed at 2,000 RPM.

8. Observe the exhaust system back

pressure reading on the gage.

Does the reading exceed the specified
value?

Go to Step 6 Go to Step 7

6

Inspect the exhaust system for the
following conditions:

Damage in the exhaust pipe

Debris in the exhaust pipe

Muffler or resonator internal failure

Two-layer exhaust pipe separation

Did you find and correct the condition?

-

Go to Step 8

-

7

Replace the catalytic converter. Refer to
Catalytic Converter Replacement
(4.3L) or Catalytic Converter
Replacement (4.8L, 5.3L, 6.0L, 6.2L) or
Catalytic Converter Replacement
(6.6L) or Catalytic Converter
Replacement - Left Side (6.0L -
Cab/Chassis).
Did you find and correct the condition?

-

Go to Step 8

-

1. Remove the J 35314-A . See Special

Tools.

2. Reinstall the HO2S. Refer to Heated

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Exhaust - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado