EXPERTEC TSB (9-92-7)

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

BLOCK LEARN AND INTEGRATOR - (USEFUL DIAGNOSTIC TOOL)

Model(s): All Oldsmobile

Bulletin No.: Oldsmobile 9-92-7

Date: 09/01/1992

SERVICE INFORMATION

As technology increases and there is a growing demand for tighter emission controls, technicians must find better ways to utilize the diagnostic information they receive from the Tech I scanner or CAMS machine. To repair difficult driveability conditions, block learn and integrator are two useful sources of diagnostic information.

Block learn and integrator give the ECM the capability to control the fuel/air ratio as close to 14.7:1 as possible. The optimum block learn and integrator is around 128. In more understandable terms, the block learn and integrator tells us the injector "on" time. Block learn and integrator are trying to make adjustments to the air/fuel ratio on fuel injected cars. For example, if the block learn/integrator is 150, the injectors are "on" longer because the oxygen sensor is looking at a lean mixture. If the block learn/ integrator is 80, the injectors are "on" less time because the oxygen sensor is looking at a rich condition.

Integrator is trying to make temporary changes to fuel delivery. It only functions in closed loop. Integrator monitors the O2 sensor voltage and adds or subtracts fuel depending on whether the O2 senses lean or rich. Integrator can correct fuel delivery over a wide range, but the correction is temporary.

Because of this temporary correction, block learn was added to the ECM software to make smaller but more permanent corrections. When the block learn is at a fixed value other than 128 +/- 10, this indicates a constant condition, either rich or lean. The following charts show some of the causes of a block learn that is too high or too low.

BLOCK LEARN HIGH 138 OR GREATER INDICATES A LEAN EXHAUST

• Faulty oxygen sensor circuit; ie. low voltage output at the O2 sensor/short to ground in the O2 wire/stripped or mistorqued O2 sensor causing loss of ground
• Injector faults; i.e. restricted with contamination, pintle stuck shut or not fully opening/electrical winding shorts or open
• Missing throttle body inlet screen on the 3.3L or 3800 engines
• Low fuel pressure; i.e. faulty pressure regulator/restricted fuel sock /faulty fuel pump/restricted fuel filter
• Vacuum leak; i.e.; PCV valve flowing too much air/cracked vacuum hoses/intake gasket leak
• Ignition misfire; i.e. high secondary resistance/coil tracking/fault in EST circuit
• Weak pick-up coil or crank sensor output
• Water in the fuel system
• EGR valve not opening

BLOCK LEARN LOW 120 OR LESS INDICATES A RICH EXHAUST

• High fuel pressure; i.e. restriction in fuel return line/loss of vacuum at fuel pressure regulator
• MAP voltage too high; i.e. loss of vacuum at MAP sensor/faulty MAP sensor
• Injector faults; i.e. leaking injector/shorted windings causing excess current flow
• Excessive fuel in the oil causing fuel to be pulled through PCV valve
• Vapor canister is full of raw fuel from possibly over filling the gas tank
• ECM may receive extra reference signals from an Electromagnetic Induction (EMI) source due to routing of ECM wiring
• False TPS voltage or voltage is too high for throttle position
• Silicone contamination of O2 sensor
• Restricted exhaust condition; i.e. faded catalytic converter due to already rich condition
• Coolant temperature fault; i.e. open in CTS wire/bad sensor