Circuit Description
The crankshaft position (CKP) sensor sends pulses to the ECM as the 58 reluctor
wheel teeth rotate past the sensor. The ECM knows the acceleration and deceleration
the crankshaft should experience under different conditions, and can constantly determine
its speed of rotation. A misfire causes an unexpected change in the crankshaft speed.
The ECM also continuously calculates the crankshaft position from the CKP sensor signals.
This information is used to determine which cylinder is misfiring so that the ECM
can increment the appropriate misfire counter and set the appropriate DTC. DTCs P0301
through P0306 correspond to cylinders 1 through 6.
DTC Parameters
DTC P0313 will set when a misfire has been detected along with the following
events:
| • | Condition exists for longer than 30 seconds. |
| • | Fuel tank contains less than 2.9 gallons of fuel. |
| • | Engine speed between 520 and 6520 RPM. |
| • | Traction control is not active. |
| • | Engine has been running more than 5 seconds. |
| • | IAT greater than -8°C (17°F). |
| • | EVAP diagnosis is not active. |
| • | No TP or CKP codes are set. |
Important: The misfire diagnostics are continually checked
with the engine running when the above conditions have been met.
P0313 is a (type D) DTC.
Diagnostic Aids
When attempting to diagnose an intermittent problem, use the Scan tool to review
malfunction history diagnostic information. This supplemental data can be used to
duplicate a problem.
If an injector, IC, or EGR DTC is active and the misfire DTC is active, diagnose
the other DTCs first.
Use the Scan tool to monitor active misfire counts. If a specific cylinder misfires
under certain load conditions, it may be duplicated in the stall.
| • | Injector resistance = 14-23 ohms. |
| • | Coil Pack Secondary Resistance = 8 to 15 K ohms. |
| • | Wire Positioning on Coils - 1,3,5 2,4,6. |
If fuel level is adequate and current misfire counters are incrementing, refer
to the appropriate misfire DTC (P0300 - P0306).
