DTC P0300: MULTIPLE CYLINDER MISFIRE DETECTED
The powertrain control module (PCM)/engine control module (ECM) monitors crankshaft and camshaft position to detect if engine is misfiring. The PCM/ECM looks for a quick drop in crankshaft speed. This test is executed in blocks of 100 camshaft revolution tests. It may take between one to several tests to store a Diagnostic Trouble Code (DTC) and illuminate Malfunction Indicator Lamp (MIL). Under light misfire conditions, it may also take more than one trip to set a DTC Severe misfire will flash MIL indication that catalyst damage is possible. The Torque Converter Clutch is disabled momentarily to determine if misfire was due to a rough road condition (automatic transaxle only).
Conditions For Setting DTC
? DTCs P0106, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0336, P0337, P0341, P0342, and P0502 not set
? Engine run time is greater than or equal to 5 seconds.
? A/C compressor clutch has not just engaged or disengaged.
? Engine load and engine speed is in a detectable region and is at or above zero torque.
? Camshaft position (CMP) sensor is in synchronization.
? Exhaust Gas Recirculation (EGR) flow diagnostic is not in progress.
? Fuel level is greater than 10% rated tank capacity.
? Decel Fuel Cutoff (DFCO) is not active.
? Fuel is not shutoff from high engine speed of 6200 rpm for M/T or 6300 rpm for A/T in drive and 4100 rpm in park for A/T vehicle.
? Fuel is not shutoff at 255 mph (410 km/h).
? An automatic transmission is not shifting.
? Pulse throttle position change is less than 2.73% per 100 ms.
? Minus throttle position change is less than 2.73% per 100 ms.
? Have not encountered an abusive engine speed of 6313 rpm for M/T and 6406 rpm for A/T vehicles
? Engine acceleration is less than or equal to 13 consecutive powerstrokes.
? Engine deceleration is less than or equal to 11 for A/T and 12 for M/T vehicle consecutive powerstrokes.
? Throttle position is greater than 3.125% when vehicle speed is greater than 10 mph (16 km/h).
? 30 engine cycled have occurred since cranking has started.
? Engine speed is between 688 and 6156 rpm.
? Vehicle voltage is between 11 and 16 volts.
? Coolant temperature is between -7 C (19.4 F) and 120 C (248 F).
? The torque converter clutch is not forced on because transaxle is overheating while misfire
diagnosis is requesting to disable torque converter clutch.
? The engine speed is less than or equal to 2000 rpm, or crank angle sensing error has been learned.
? Crankshaft speed patterns are normal.
? There is correct ratio between Crankshaft Position (CKP) Sensor pulses and Camshaft Position (CMP) Sensor pulses.
Action Taken When DTC Sets
? The MIL will illuminate after two consecutive ignition cycles in which diagnostic runs with fault active.
? The MIL will illuminate immediately and flash if misfire is present (automatic only).
? The PCM/ECM will record operating conditions at time diagnostic fails. This information will be stored in Freeze Frame and Failure Records buffers.
? A history DTC is stored.
Conditions For Clearing MIL/DTC
? The MIL will turn off after three consecutive ignition cycles in which diagnostic runs without a fault within freeze frame conditions that DTC failed.
? A history DTC will clear after 40 consecutive warm up cycles without a fault.
? The DTC(s) can be cleared by using scan tool.
An intermittent can also be result of a defective reluctor wheel. Remove CKP sensor and inspect reluctor wheel through sensor mount hole. Check for porosity and condition of wheel. If DTC is intermittent refer to "Symptom Diagnosis".
Number(s) below refer to step number(s) on Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts technician to complete some basic checks and to store freeze frame and failure records data on scan tool if applicable. This creates an electronic copy of data taken when malfunction occurred. The information is then stored on scan tool for later reference.
3. A visual/physical inspection should include checking following components:
? The wiring for proper connections, pinches or cuts.
? The PCM/ECM grounds for being clean and tight.
? The vacuum hoses for splits, kinks, and improper connections as shown on Vehicle Emission Information label.
? Check thoroughly for any type of leak or restriction.
? Check for air leaks at throttle body mounting area and intake manifold sealing surfaces.
5. When all accumulators are relatively equal, then misfire is being caused by something that affects entire engine. When they are not, then misfire is being caused by something that is specific to two or more cylinders.
6. Whenever misfire is not present, operating vehicle may be necessary to duplicate conditions in Freeze Frame Data in order to detect misfire. Depending on engine load, conditions may have to be maintained for up to 20 seconds. Whenever misfire accumulators start to increment, then misfire is present. A history misfire counter will store number of misfires that have occurred until DTC is cleared.
7. 8. Check fuel for water, alcohol, etc.
9. 9. A basic engine problem that affects all cylinders is only possibility at this point (Cam timing throttle body leak, restricted air flow, etc.).
10. 11. Tests ignition system voltage output using a spark tester.
11. 12. Replace any spark plugs that are worn, cracked or fouled.
12. 13. Checks for voltage at ignition feed circuit.
13. 18. Whenever driver circuit is shorted to ground, light will be on steady. When driver circuit is shorted to voltage or open, light will be off.
14. 19. Since voltage is supplied to fuel injector on a single circuit, malfunction can only be a poor connection or open in fuel injector harness. An open before harness would result in a "Engine Cranks But Will Not Run" complaint.
27. Before replacing PCM/ECM, check terminals for improper mating, broken locks, or physical damage to wiring harness. The replacement PCM/ECM must be reprogrammed.
Thursday, March 26th, 2009 AT 10:02 PM