Exhaust System Back Pressure Test Tool (04 12 00)

Publication date: 2000-11-01
Reference number: 04 12 00

EXHAUST SYSTEM BACK PRESSURE TEST TOOL

TECHNICAL SERVICE BULLETIN

Reference Number(s): 04 12 00, Date of Issue: November, 2000

BMW:	All Models
GROUP:	04 - Tools and Equipment

SUBJECT

Exhaust System Back Pressure Test Tool

SITUATION

Distribution of the following tool will be through the Automatic Tool Shipment Program. Additional tools may be purchased through your PDC.

TOOL INFORMATION

Exhaust System Back Pressure Test Tool P/N 99 00 0 001 855

Fig 1: Exhaust System Back Pressure Test Tool

Used to check exhaust system for excessive back pressure in regards to customer complaint of engine has no power or check engine lamp illuminated (FC 40, 45, 233 and/or 63 74. Refer to SIB 18 02 99 and repair manual section 11 78 for complete details. Attached to this bulletin are test instructions. Identical instructions are included with each tool.

The exhaust back pressure tool consists of:

1. Analog gauge
2. Connecting hose
3. Connecting fitting for oxygen sensor hole

TOOL WARRANTY

Refer to Pats Information bulletin 01 01 95 for tool warranty details.

EXHAUST BACK PRESSURE TEST INSTRUCTIONS

PROCEDURE

If the above customer complaints are received and a restricted catalytic converter is suspected:

Remove the pre-catalytic converter oxygen sensor as outlined in the appropriate repair manual, group 11 section 11 78.
Install the exhaust back pressure gauge hose connector in place of the pre-catalytic converter oxygen sensor. See Fig 2 .
NOTE: Lightly tighten (snug) the tool fitting. Do not over tighten.

Fig 2: Exhaust Back Pressure Gauge Hose Connector Installation
Mount the gauge in an upright position - the hose connection must be located at the bottom of the gauge for proper back pressure readings. See Fig 3 .
NOTE: Incorrect test readings will be the result if the gauge is not in the upright position, for example: hung up side down, laid flat, etc.

Fig 3: Gauge Mounted In Upright Position
With the hand brake on and the vehicle in park or neutral, start the engine. The engine must be at operating temperature before measurements are taken.
Raise and briefly hold the engine speed at 2500 rpm. With the engine speed stabilized at 2500 rpm the gauge should remain in the green zone.
Test Results:
- If the gauge indicates readings in the green zone (less than 1.5psi) the catalytic converter is not restricted.
  NOTE: A restricted catalytic converter will typically indicate readings greater than 2psi during the 2500 rpm test as described above.
  
  Fig 4: Gauge Reading Indicating Acceptable Back Pressure
- If the gauge indicates readings beyond the green zone (greater than 1.5psi) the catalytic converter is restricted and should be replaced.
  NOTE: A restricted catalytic converter will typically indicate readings greater than 2psi during the 2500 rpm test as described above.
  
  Fig 5: Gauge Reading Indicating Excessive Back Pressure
Notes:
1. When revving the engine rapidly from idle speed to 3000-4000 rpm the gauge may momentarily indicate a reading beyond the green zone (up to approximately 2psi).
2. Also if the vehicle is driven with the gauge connected (not recommended) it will display readings beyond the green zone during engine acceleration (high engine load).
3. A gauge reading beyond the green zone (greater than 1.5psi) is normal under these conditions due to the momentary back pressure build up in the exhaust system caused by the engine acceleration and does not indicate a restricted catalytic converter.
Reinstall the oxygen sensor as outlined in the repair manual, group 11 section 11 78 and clear all fault codes in the ECM/DME memory.