Focus Fanatics - View Single Post - DTC Codes (Detailed Descriptions)
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Old 09-14-2005, 03:30 PM   #2
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P0231 - Fuel Pump Secondary Circuit Low NOTE: For natural gas applications, the following description applies to the fuel shutoff valve monitor (FSVM) and the fuel shutoff valve power (FSV PWR) circuits.
The PCM monitors the fuel pump monitor (FPM) circuit. The test fails if the PCM commands the fuel pump ON and B+ voltage is not detected on the FPM circuit. Open B+ circuit to the fuel pump relay
Open FP PWR circuit between the fuel pump relay and its connection to the FPM circuit
Damaged fuel pump relay
Damaged PCM (engine will start)
For 4.6L Mustang, open FP PWR circuit from low speed fuel pump relay, through resistor to FPM splice (engine will start)
For 5.4L SC Lightning, damaged IFS switch, IFS switch relay, or concern with related circuits.
During KOEO self-test, the PCM will command the fuel pump ON so this test can be performed.

P0232 - Fuel Pump Secondary Circuit High NOTE: For natural gas applications, the following description applies to the fuel shutoff valve monitor (FSVM) and the fuel shutoff valve power (FSV PWR) circuits.
The PCM monitors the fuel pump monitor (FPM) circuit. This test fails when the PCM detects voltage on the FPM circuit while the fuel pump is commanded OFF. The FPM circuit is wired to a pull-up voltage inside the PCM. The FPM circuit will go high if, with the key ON and the fuel pump commanded OFF, the FPM/FP PWR circuit loses its path to ground through the fuel pump. The FPM circuit will also go high if the FPM/FP PWR circuit is shorted to power.
Inertia fuel shutoff (IFS) switch not reset or electrically open
Open circuit between the fuel pump and the FPM connection to the FP PWR circuit
Poor fuel pump ground
Fuel pump electrically open
Fuel pump secondary circuits short to power
Fuel pump relay contacts always closed
Open FPM circuit between PCM and connection to FP PWR circuit
Damaged low speed fuel pump relay or concern with related circuits (if equipped).
Damaged PCM
Continuous memory P0232 can be set if the IFS switch was tripped, then reset, or if the fuel pump circuit is activated when the PCM expected the circuit to be off (i.e. fuel system test or prime procedure).

P0234 - Supercharger Overboost Condition The PCM disables (bypasses) the supercharger boost and sets a diagnostic trouble code (DTC) to keep from damaging the powertrain (engine or transmission) during potential harmful operating conditions. Brake torque (brake on and throttle at wide open)
Transmission oil temperature (TOT) exceeds calibrated threshold
Engine over temperature
Ignition misfire exceeds calibrated threshold
Knock sensor (KS) failure or knock detected
Low speed fuel pump relay not switching
Check for other diagnostic trouble codes accompanying the P0234 or check appropriate and available PIDs related to above possible causes.

P0243 - Supercharger (Boost) Bypass Solenoid Circuit Malfunction The PCM monitors the supercharger (boost) bypass (SCB) solenoid circuit for an electrical failure. The test fails when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified SCB solenoid duty cycle (100% or 0%) by PCM command. VPWR circuit open to SCB solenoid
SCB solenoid circuit shorted to PWR GND or CHASSIS GND
Damaged SCB solenoid
SCB solenoid circuit open
SCB solenoid circuit shorted to VPWR
Damaged PCM
Disconnect SCB solenoid. Connect test lamp to SCB solenoid harness connector. Cycle SCB driver in PCM by Output Test Mode. Test lamp cycle on and off - SCB solenoid is suspect. Test lamp always on - SCB signal short in harness or PCM. Test always off - SCB signal or VPWR open in harness or PCM.

P0298 - Engine Oil Over Temperature Condition Indicates the Engine Oil Temperature Protection strategy in the PCM has been activated. This will temporarily prohibit high engine speed operation by disabling injectors, therefore reducing the risk of engine damage from high engine oil temperature. Note: On engines which are equipped with an oil temperature sensor, the PCM reads oil temperature to determine if it is excessive. When an oil temperature sensor is not present, the PCM uses an oil algorithm to infer actual temperature. Engine shutdown strategy function is the same on vehicles with and without oil temperature sensors. Very high engine rpm for extended period of time.
Over-heating condition.
Malfunction EOT sensor or circuit (vehicles w/EOT sensor).
Base engine concerns.
Engine operating in high rpm range, due to improper gear selection. May cause Lack/Loss of Power or Surge customer concern.

P0300 - Random Misfire The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring. Camshaft position sensor (CMP)
Low fuel: less than 1/8 tank
Stuck open EGR valve
Blocked EGR passages
One or more EGR passages may be blocked or partially blocked. If this is the case the Misfire Detection Monitor will indicate the EGR port to check for possible blockage.

P0301 through P0310 - Misfire Detection Monitor The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. Ignition system
Fuel injectors
Running out of fuel
EVAP canister purge valve
Fuel pressure
Evaporative emission system
Base engine
The MIL will blink once per second when a misfire is detected severe enough to cause catalyst damage. If the MIL is on steady state, due to a misfire, this will indicate the threshold for emissions was exceeded and cause the vehicle to fail an inspection and maintenance tailpipe test.

P0320 - Ignition Engine Speed Input Circuit Malfunction The ignition engine speed sensor input signal to PCM is continuously monitored. The test fails when the signal indicates that two successive erratic profile ignition pickup (PIP) pulses have occurred. Loose wires/connectors.
Arcing secondary ignition components (coil, wires and plugs)
On board transmitter (2-way radio)
The DTC indicates that two successive erratic PIP pulses occurred.

P0325 - Knock Sensor 1 Circuit Malfunction (Bank 1) See DTC P0326

P0326 - Knock Sensor 1 Circuit Range/ Performance (Bank 1) The knock sensor detects vibrations upon increase and decrease in engine rpm. The knock sensor generates a voltage based on this vibration. Should this voltage go outside a calibrated level a DTC will set. Knock sensor circuit short to GND
Knock sensor circuit short to PWR
Knock sensor circuit open
Damaged knock sensor
Damaged PCM
A knock sensor voltage greater than 0.5V with the key ON and engine OFF indicates a hard fault.

P0330 - Knock Sensor 2 Circuit Malfunction (Bank 2) See DTC P0331

P0331 - Knock Sensor 2 Circuit Range/performance (Bank 2) The knock sensor detects vibration upon increase and decrease in engine rpm. The knock sensor generates a voltage based on this vibration. Should this voltage go outside a calibrated level a DTC will set. Knock sensor circuit short to GND
Knock sensor circuit short to PWR
Damaged knock sensor
Damaged PCM
Knock sensor circuit open
A knock sensor voltage greater than 0.5V with the key ON and engine OFF indicates a hard fault.

P0340 - Camshaft Position (CMP) Sensor Circuit Malfunction The test fails when the PCM can no longer detect the signal from the CMP sensor. CMP circuit open
CMP circuit short to GND
CMP circuit short to PWR
SIG RTN open (VR sensor)
CMP GND open (Hall effect sensor)
CMP misinstalled (Hall effect sensor)
Damaged CMP sensor shielding
Damaged CMP sensor
Damaged PCM
Harness routing, harness alterations, improper shielding, or electrical interference from other improperly functioning systems may have intermittent impact on the CMP signal.

P0350 - Ignition Coil (Undetermined) Primary/ Secondary Circuit Malfunction Each ignition primary circuit is continuously monitored. The test fails when the PCM does not receive a valid IDM pulse signal from the ignition module (integrated in PCM). Open or short in Ignition START/RUN circuit
Open coil driver circuit
Coil driver circuit shorted to ground
Damaged coil
Damaged PCM
Coil driver circuit shorted to VPWR

P0351 Through P0360 - Ignition Coil A through J Primary/ Secondary Circuit Malfunction Each ignition primary circuit is continuously monitored. The test fails when the PCM does not receive a valid IDM pulse signal from the ignition module (integrated in PCM). Open or short in Ignition START/RUN circuit
Open coil driver circuit in harness
Coil driver circuit shorted to ground
Damaged coil
Damaged PCM
Coil driver circuit shorted to PWR

P0400 EGR Flow Failure (outside the minimum or maximum limits) The EEGR system is monitored once per drive cycle during steady state conditions above 48 mph . The test will fail when a malfunction is detected by PCM calculations indicating the EGR flow is less or greater than expected. EEGR valve stuck open or closed
Connector to EEGR not seated
EEGR motor windings shorted or open circuited
No power to EEGR
Harness open or shorted to power or ground
Vacuum signal to MAP restricted or leaking
MAF sensor signal erroneous
Damaged PCM
Carbon build up in EEGR valve seat area
One or more sensor not responding or out of range
All of the following sensors input data to the PCM for proper operation of the EEGR system: ECT, CPS, IAT, MAF, TP, MAP. Any DTC relating to these sensors must be resolved prior to addressing

P0400 code.

P0401 - EGR Flow Insufficient Detected The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum. Vacuum supply
EGR valve stuck closed
EGR valve leaks vacuum
EGR flow path restricted
EGRVR circuit shorted to PWR
VREF open to D.P.F. EGR sensor
D.P.F. EGR sensor downstream hose off or plugged
EGRVR circuit open to PCM
VPWR open to EGRVR solenoid
D.P.F. EGR sensor hoses both off
D.P.F. EGR sensor hoses reversed
Damaged EGR orifice tube
Damaged EGRVR solenoid
Damaged PCM
Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents.

P0402 - EGR Flow Excessive Detected The EGR system is monitored for undesired EGR flow during idle. The EGR monitor looks at the DPF EGR signal at idle and compares it to the stored signal measured during key ON and engine OFF. The test fails when the signal at idle is greater than at key ON engine OFF by a calibrated amount. EGR valve stuck open
Plugged EGR vacuum regulator solenoid vent
Plugged EGR tube
Slow responding D.P.F. EGR sensor
Damaged DPF EGR sensor
Improper vacuum hose connection
Plugged vacuum hoses
EGRVR circuit shorted to ground
Damaged EGR vacuum regulator solenoid
Damaged PCM
A DPFEGR PID reading that is greater at idle than during key ON and engine OFF by 0.5 volt or a rough engine idle, may indicate a hard fault.

P0403 EEGR Electric Motor Windings Or Circuits To The PCM Shorted Or Open The EEGR system is continously monitored to check the 4 EEGR motor coils, circuits, and the PCM for opens, shorts to power and ground. If a malfunction is detected the EEGR system will be disabled and additional monitoring will be suspended for the remainder of the drive until the next drive cycle. EEGR motor windings open
Connector to EEGR not seated
Open circuit in harness from PCM to EEGR
Open circuit in PCM
Short circuit in EEGR motor
Short circuit in harness from PCM to EEGR
Short circuit in PCM
If an intermittent condition is suspected the most effective methoid of wiring fault isolation is to use the wiggle test methoid while measuring for shorts and open circuits.

P0411 - Secondary Air Injection (AIR) system upstream flow See DTC P1411

P0412 - Secondary Air Injection System (AIR) circuit malfunction The PCM attempts to control when air is injected in the exhaust. The DTC indicates a Secondary Air injection system AIR circuit fault. AIR circuit open
AIR bypass solenoid fault
Damaged PCM
AIR circuit short to power
Solid state relay fault
Damaged AIR pump
The AIR circuit is normally held high through the AIR bypass solenoid and SSR when the output driver is off. Therefore, a low AIR circuit indicates a driver is always on and a high circuit indicates an open in the PCM.

P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold Use of leaded fuel
Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timing
Compare HO2S upstream and downstream switch rate and amplitude. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S very slow and reduces the amplitude of those switches as compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly with increase amplitude, approaching the switching rate and amplitude of the upstream HO2S. Once beyond an acceptable limit the DTC is set.

P0430 - Catalyst System Efficiency Below Threshold (Bank 2) Indicates Bank 2 catalyst system efficiency is below the acceptable threshold. Use of leaded fuel
Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timing
Compare HO2S upstream and downstream switch rate and amplitude. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S very slow and reduces the amplitude of those switches as compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly with increase amplitude, approaching the switching rate and amplitude of the upstream HO2S. Once beyond an acceptable limit the DTC is set.

P0442 - EVAP Control System Leak Detected (Small Leak) The PCM monitors the complete EVAP control system for presence of a small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 1.016 mm (0.04 inch) is detected by the EVAP running loss monitor test. After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications
Small holes or cuts in fuel vapor hoses/tubes
Canister vent solenoid stays partially open on closed command
Damaged, cross-threaded or loosely installed fuel filler cap
Loose fuel vapor hose/tube connections to EVAP system components
EVAP system component seals leaking (EVAP canister purge valve, fuel tank pressure sensor, canister vent solenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly)

P0443 - EVAP Control System Canister Purge Valve Circuit Malfunction The PCM monitors the EVAP canister purge valve circuit for an electrical failure. The test fails when the signal moves outside the minimum or maximum allowable calibrated parameters for a specified purge duty cycle by PCM command. VPWR circuit open
EVAP canister purge valve circuit shorted to GND
Damaged EVAP canister purge valve
EVAP canister purge valve circuit open
EVAP canister purge valve circuit shorted to VPWR
Damaged PCM
Monitor EVAPPDC PID and voltage between EVAP canister valve signal and PWR GND in output test mode with key ON engine OFF (or in key ON engine RUNNING mode). EVAPPDC PID at 0% and voltage less than 1.0 volts (or EVAPPDC PID at 100% and voltage less than 0.5 volts) indicates a hard fault.

P0451 - FTP Sensor Circuit Noisy The fuel tank pressure changes greater than 14 inches of H 2 0 in 0.10 seconds. Intermittent open or short in the FTP sensor or the FTP sensor signal.
Monitor FTP PID and does it change from above 15 inches of H 2 0 to below a minus (-) 15 inches of H 2 0 often in 1.0 minute.

P0452 - FTP Sensor Circuit Low Voltage Detected The PCM monitors the EVAP control system FTP sensor input signal to the PCM. The test fails when the signal average drops below a minimum allowable calibrated parameter. Contamination internal to FTP sensor connector
Damaged PCM
FTP circuit shorted to GND or SIG RTN
Damaged FTP sensor
FTP V PID reading less than 0.22 volt with key ON and engine OFF or during any engine operating mode indicates a hard fault.

P0453 - FTP Sensor Circuit High Voltage Detected The PCM monitors the EVAP control system FTP sensor input signal to the PCM. The test fails when the signal average jumps above a minimum allowable calibrated parameter. FTP circuit open
VREF shorted to VPWR
Damaged PCM
FTP circuit shorted to VREF or VPWR
SIG RTN circuit open
Damaged FTP sensor
FTP V PID reading greater than 4.50 volts with key ON and engine OFF or during any engine operating mode indicates a hard fault.

P0455 - EVAP Control System Leak Detected (No Purge Flow or Large Leak) The PCM monitors the complete EVAP control system for no purge flow, the presence of a large fuel vapor leak or multiple small fuel vapor leaks. The system failure occurs when no purge flow (attributed to fuel vapor blockages or restrictions), a large fuel vapor leak or multiple fuel vapor leaks are detected by the EVAP running loss monitor test with the engine running (but not at idle). After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications
Disconnected or cracked fuel EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube
EVAP canister purge valve stuck closed
Damaged EVAP canister
Damaged or missing fuel filler cap
Insufficient fuel filler cap installation
Loose fuel vapor hose/tube connections to EVAP system components
Blockages or restrictions in fuel vapor hoses/tubes (items also listed under disconnections or cracks)
Fuel vapor control valve tube assembly or fuel vapor vent valve assembly blocked
Canister vent (CV) solenoid stuck open
Mechanically inoperative fuel tank pressure (FTP) sensor
Check for audible vacuum noise or significant fuel odor in the engine compartment or near the EVAP canister and fuel tank.

P0456 - EVAP Control System Leak Detected (Very Small Leak) The PCM monitors the complete EVAP control system for the presence of a very small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 0.508 mm (0.020 inch) is detected by the EVAP running loss monitor test. Very small holes or cuts in fuel vapor hoses/tubes.
Loose fuel vapor hose/tube connections to EVAP system components.
EVAP system component seals leaking (refer to Possible Causes under DTC P0442).
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