Diagnostic Aids

DTC indicates excessive engine noise usually caused by something else besides spark knock. It does not indicate a faulty knock sensor circuit subsystem. Knock could be caused by valve lifter noise, belt tensioner, loose bracket, low octane fuel, heavy load or scuffed piston/cylinder bore.

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 reduced power condition may result due to maximum spark retard.

The spark compensating cells will eventually learn back (to 0) when knock condition is corrected. The spark compensating cells may be viewed on the scan tool's spark table. The stored spark retard (hi, mid and low table values) are adjusted according to start up coolant temperature. If coolant temperature is:

• Less than 46°F (8°C) - Table cells/value is set to 0.
• Less than 133°F (56°C) - Table value is 75 percent of stored learned values.
• Greater than 219°F (104°C) - Use stored value.