The document discusses the importance of performing baseline emission tests before and after vehicle repairs using various equipment such as a 5-gas analyzer, scope, scan tool, or DVOM. A baseline test involves monitoring the 5 regulated emissions gases at idle, 3000 RPM, and two modes of the Accelerated Simulation Mode to establish a starting point for emissions levels. Comparing the before and after repair baseline readings allows technicians to determine if a repair was successful by calculating the percentage reduction in emissions.

1.  Why baseline
 Before and after repairs
 Baselining with a 5 gas analyzer
 Baselining with a scope, scan tool, or DVOM
 Correlation of baseline reading with Bar „97 test
results

2.  Diagnosing an emission failure is different
from many auto repairs
 Sometimes a vehicle will “run fine” but fail a
smog test
 It can be hard for a tech or customer to
visualize a smog failure

3.  A baseline test consists of:
 Monitoring all 5 gases at:
 Stabilized operating temperature
 Idle
 3000 RPM (no load)
 ASM mode 1
 ASM mode 2

4.  Performing a baseline test before and after a
repair will be an indication of how successful
your repair was
 Sometimes a repair of one gas will raise
another gas out of limits
 Remember you are going to compare the two
sets of readings, so always perform a before
and after baseline test exactly the same, or
results will be inaccurate

5.  Analyze the “after repair” baseline readings
and the “before repair” baseline readings by
comparing the two sets of readings.
 Calculate the difference in percentages
 If the percentage of reduction is the same or
higher (cleaner)
 Your repair was probably successful
 Be sure to check the other gas readings

6. Equipment used to gather baseline readings
 DVOM
 Hook up to 02 sensor
 Positive lead to 02 sensor return wire
 Negative lead to good ground
 Scan tool
 Hook up and program

7.  DVOM to fuel injector (if no data stream)
 Positive lead to fuel injector ground
 Negative lead to good ground
 Set on ms scale
 Warm up vehicle
 Monitor the O2 ( voltage & frequency) and the
Injector (pulse width) simultaneously.
 O2 should fluctuate above and below .450 volts at
least once every couple of seconds
 A rich exhaust must = a lean command

8.  If 02 sensor reading is biased high or low you
have a problem (may not be 02 sensor)
 Baselining using the 02 sensor and M/C
command will monitor CO only

9.  A digital storage oscilloscope (DSO) will give
more accurate information
 If a small misfire is present more oxygen is in
the exhaust stream
 The 02 sensor wave form will have a higher
frequency
 Using this method only CO & HC problems
can be identified

10.  BAR „97 analyzer
 Road test -- put on analyzer
 Monitor and record all 5 gases during 4 conditions
mentioned before
 Other test equipment utilized during this baseline
test may include timing light, DSO, Digital
Pyrometer etc.

11.  Special note: If all OEM emissions equipment is
not hooked up and operating as
designed, baseline test results will be
inaccurate. (missing, modified or disconnected
emission systems must be repaired first!)