SW1 L4-1.9L SOHC VIN 8 (1996)
Knock Sensor: Customer Interest
Engine - Lack of Power/DTC P0326 Set
BULLETIN: 01-T-12
ISSUE DATE: March, 2001
CATEGORY TYPE: Engine-04
CATEGORY: Emission Controls
CORPORATION No.: 01-06-04-013
SUBJECT:
Intermittent Lack Of Power and/or DTC P0326 (Replace Camshaft - P/N 21007289, If Necessary and Replace Knock Sensor - P/N 21025126)
MODELS AFFECTED:
1996 - 1997 Saturn S-Series vehicles equipped with SOHC engines (RPO L24)
CONDITION:
Some customers may comment about an intermittent lack of power on acceleration on vehicles equipped with SOHC (L24) engines. This condition is
most likely to occur on a vehicle which has had a cylinder head replacement.
CAUSE:
This condition may be caused by the knock sensor picking up noises within a certain frequency and during specific engine conditions that the PCM may
incorrectly interpret as spark knock. The PCM will retard spark advance in an attempt to eliminate the perceived spark knock. If this reduction in spark
advance is great enough, the driver will perceive a loss of power from the vehicle.
This condition can result from several different causes, however the two primary causes addressed by this bulletin are:
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Noise occurring as the intake valve closes or momentarily bounces against the valve seat, and/or;
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Normal engine noises (not spark knock) which cause the PCM to unnecessarily retard spark timing.
CORRECTION:
Refer to the procedure in this bulletin for corrective action.
PROCEDURE
1.
Evaluate vehicle under the conditions described by the customer. This condition may be very intermittent and difficult to reproduce. This
condition is most likely to occur with the engine at normal operating temperature, under light to moderate load, under light to moderate throttle,
and engine speed between 1500 - 2000 rpm.
2.
Using a Scan tool, monitor the following parameters in the SPARK CONTROL screen under the Engine Data Display:
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LOW SPARK MODIFIER
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MID SPARK MODIFIER
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HIGH SPARK MODIFIER
If any or all of the SPARK MODIFIERS increase above 6.0 and the lack of power is experienced proceed to next step.
If none of the SPARK MODIFIERS show any activity or there is some activity but the values stay in the lower (below 4.0) range and are
intermittent, the condition may not be corrected by the parts and procedures in this bulletin. Refer to additional diagnostic information (Low
Power, Spark Knock, or DTC P0326) in the appropriate model year Powertrain Controls service manual.
3.
Camshaft identification number must be located and read.
4.
Remove cylinder head rocker cover. (Refer to "SOHC (L24) Cylinder Head Removal" procedure in the appropriate model year Engine/Fuel/Air
Intake/Exhaust service manual for rocker cover removal information.)
