GM Service Manual Online
For 1990-2009 cars only

Object Number: 16621  Size: SH
(1)Back Pressure Gauge
(2)Heated Oxygen Sensor (HO2S)
(3)Exhaust Pipe

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Carefully remove a preconvertor Heated Oxygen Sensor (HO2S). Refer to Heated Oxygen Sensor Replacement .
  2. Install the exhaust backpressure tester J 35314-A in place of the HO2S.
  3. Start the engine.

Is the reading more than the specified value?

8.6 kPa (1.25 psi)

Go to Step 4

Go to Step 3

3

  1. Increase the engine speed to the first specified value.
  2. Observe the backpressure gauge.

Does the reading exceed the second specified value?

2000 RPM

20.7 kPa (3 psi)

Go to Step 4

Go to Step 6

4

  1. Check the exhaust system for a collapsed pipe, internal muffler failure, or any kind of heat distress. Refer to Exhaust System Inspection in Engine Exhaust.
  2. Repair as necessary.

Did you find a problem?

--

Go to Step 6

Go to Step 5

5

Replace the catalytic converter. Refer to Catalytic Converter Replacement in Engine Exhaust.

Is the action complete?

--

Go to Step 6

--

6

Operate the vehicle within the conditions under which the original symptom was noted.

Does the system now operate properly?

--

System OK

Go to Step 2