Flag 53

Circuit Schematic:

KNOCK SENSOR CIRCUIT - KNOCK PRESENT
The purpose of this information flag is to indicate excessive engine noise. The knock sensor cannot differentiate between spark knock and other engine noise. When the knock sensor cannot eliminate noise by retarding timing, information flag 53 will be set.

INFORMATION FLAG PARAMETERS

Information flag 53 will set if:
^ If the PCM cannot reduce engine noise by retarding timing (i.e. the engine noise is most likely not due to spark knock).

DIAGNOSTIC AIDS
Information flag 53 indicates excessive engine noise usually caused by something else besides spark knock. It does not indicate a faulty knock sensor circuit subsystem.

POSSIBLE CAUSES:
^ Valve lifter noise
^ Belt tensioner
^ Loose bracket
^ Low octane fuel in high ambients while pulling loads
^ Piston/Cylinder bore scuffed

NOTE: Information flags should he used for diagnostic purposes only. They do not necessarily indicate component malfunction/failure.

The PCM has the ability to learn spark retard. If knock is present long enough to fill the mid, hi and low spark compensating cells a low power condition may result due to maximum spark retard. The 5 spark compensating cells will eventually learn back when knock condition is corrected, however, this is a slow process. The spark compensating cells may be quickly cleared by disconnecting the power to the PCM when the knock condition has been corrected.

The spark compensating cells may be viewed on the Saturn Portable Diagnostic (Scan) (PDT) Tool spark table.

The stored spark retard (hi, mid, & low table values) are adjusted according to start-up coolant temperature:

If coolant temperature is:
- Below 8°C (46°F) we set table values to 0.

- Below 56°C (133°F) we set table values to 75% of stored earned values.

- Above 104°C (219°F) we use the stored values.

- Temperatures in between are adjusted on a percentage value.