Hummer H2. Manual - part 41

distinguish itself from gear noise by occurring in all driving modes. Noise will persist with transmission in 
neutral while vehicle is moving at problem speed.  

If vehicle displays this noise condition, remove suspect axle shafts and replace axle bearings. Re-evaluate 
vehicle for noise before removing any internal components.  

VIBRATION 

Vibration is a high-frequency trembling, shaking or grinding condition (felt or heard) that may be constant or 
variable in level and con occur during the total operating speed range of the vehicle.  

The types of vibrations that can be felt in the vehicle can be divided into 3 main groups:  

z

Vibrations of various unbalanced rotating parts of the vehicle.  

z

Resonance vibrations of the body and frame structures caused by rotating of unbalance parts.  

z

Tip-in moans of resonance vibrations from stressed engine or exhaust system mounts or driveline flexing 
modes.  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Drive Axle Noise Diagnosis

  

DRIVE CYCLES 

OBD-II Vehicles - OBD-II Readiness Monitors 

* PLEASE READ THIS FIRST * 

ACURA 

For drive cycle test procedures, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.  

CHRYSLER/JEEP 

1995 FCC PCM 

2.0L FWD FCC PCM Equipped Vehicles 

The following procedure has been established to assist technicians in the field with enabling and running OBD-
II Monitors on 1995 Avenger, Neon, Sebring & Talon 2.0L models equipped with FCC PCM. The order listed 
in the following procedure is intended to allow the technician to effectively complete each monitor and to set 
the CARB Readiness Status in the least time possible.  

Upstream O2S Monitor 

Perform the following:  

z

Ensure engine is at normal operating temperature, above 170°F. 

NOTE:

This article applies to OBD-II equipped vehicles only. 

NOTE:

Some manufacturers do not provide a specific drive cycle test procedure. Some 
manufacturers include drive cycle procedures as part of self-diagnostics. 
Always check appropriate Self-Diagnostics or Testing W/Codes article for 
information related to drive cycle testing procedures. Some manufacturers may 
incorporate readiness testing as a part of the DTC test. 

NOTE:

A number of vehicles have had recalls related to "Readiness Monitor" issues, or 
may have testability issues. Some vehicles may not be testable for emission 
controls. See VEHICLE RECALLS, TESTABILITY ISSUES & VEHICLES 
CURRENTLY NOT TESTABLE for details on these vehicles. 

NOTE:

Drive cycles for Acura models are also known as "System Readiness Codes". 

NOTE:

For 1995-99 models, also see TSB 25-02-98 NON TURBO GAS ENGINE I/M OBDII 
"CARB" READINESS MONITOR INFORMATION . 

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors

  

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors

  

z

Operate the vehicle for a period of time, more than 2 minutes, at a speed above 25 MPH.  

z

Bring the vehicle to a complete stop, with foot on the brake and transaxle in gear (A/T) or neutral (M/T).  

The monitor should run while vehicle is stopped with the engine idling. Wait for a few minutes to allow the 
monitor to complete before turning off engine. 

Downstream O2 Monitor 

Perform the following:  

z

Ensure engine is at normal operating temperature, above 170°F.  

z

Decel Fuel Shut-off is Active.  

z

Minimum Engine RPM = 1600 RPM.  

z

Upstream O2S is less than .471 volts.  

The PCM begins the Downstream O2S rationality test. The PCM looks at the Downstream O2S volts for 5 
seconds, if less than .295 volts, the test passes. If the Downstream O2S is greater than .295 volts, the test 
increments a count of 1 and the test is done again. A count of 3 will set a DTC and store Freeze Frame Data. 

Rich (High Voltage) Output Test 

Perform the following:  

z

Engine coolant temperature is above 170°F.  

z

At WOT TPS voltage for more than 2 seconds.  

z

Upstream O2S volts is above .490 volts.  

The PCM begins the Downstream O2S rationality test. The PCM looks at Downstream O2S volts for 5 seconds, 
if more than .608 volts, the test passes. If the Downstream O2S is less than .608 volts, the test increments a 
count of 1 and the test is done again. A count of 3 will set a DTC and store Freeze Frame Data. 

EGR Monitor 

Perform the following:  

z

EGR Solenoid is enabled.  

z

Vehicle speed more than 3 MPH.  

z

Time from Start/Run is more than 2:09 minutes.  

z

The Fuel Control is in Closed Loop.  

z

No Limp-In or OBD-II Monitor faults present.  

z

Purge is enabled.  

z

Engine coolant temperature more than 144°F.  

z

MAP Range during Monitor: 11.70" to 16.20". 

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors

  

z

RPM Range during Monitor: 2200 RPM to 2400 RPM.  

z

Actual TP Sensor above minimum TP Sensor Range: .295 volts to 1.0 volt.  

z

Maximum Short Term Adapt = +6%.  

z

The PCM stores the EGR on Short Term Adaptive Memory value.  

The PCM begins the monitor. The PCM turns off the EGR Solenoid. The PCM uses a modified ramp rate for 
Short Term Adaptive Memory. The PCM stores the EGR off Short Term Adaptive Memory value. The PCM 
determines the Short Term Adaptive Memory shift. Between 3% to 17% Short Term shift adaptive memory, an 
EGR Monitor passes. Less than 3% rich or more than 17% shift rich will run the test again. 3 failed tests will 
equal a 1 trip EGR Monitor Failure. 

Catalyst Monitor 

Perform the following:  

z

Engine coolant temp above 170°F.  

z

Accumulated open throttle time of 3:00 minutes.  

z

Vehicle speed above 20 MPH  

z

TP Sensor is open for 4:00 minutes (A/T) or 5:00 minutes (M/T).  

z

MAP range during monitor: 14.60" to 18.20".  

z

The RPM range during monitor: 1500 RPM to 2000 RPM.  

z

Time spent in MAP and RPM ranges should be more than 3.9 seconds.  

z

No Limp-In or OBD-II Monitor faults present.  

The PCM begins the monitor. The PCM starts a timer and counts the Upstream O2S switches and counts the 
Downstream O2S switches until 20 seconds is reached. After 20 seconds is reached, the PCM divides the 
Downstream O2S switches by the Upstream O2S switches to determine the switching frequency. If it is less 
than the calibrated amount, the catalyst monitor passes. If it is more than the calibrated amount, the test 
increments a count of 1 and the test is done again. A count of 2 will cause the monitor to fail 1 trip and store 
Freeze Frame Data.  

Purge Flow Monitor 

Perform the following:  

z

A Purge Free Cell Update must take place.  

z

A/T transmission is in gear at idle, Cell 12, or M/T is in Cell 13.  

To perform a Purge Free Cell Update:  

NOTE:

If the vehicle speed drops below 20 MPH or the throttle is closed, the timer 
counts back down until the vehicle speed is above 20 MPH, then the counter 
resumes counting up again. 

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors