Hello all,

My truck is a 96 f150 with a 5.0. So just recently my engine has started to run rough. Its vibrating like it has a misfiring cylinder, but it doesn’t. Around the same time, my rear fuel pump stopped working, but the fuel gauge still works. I’m not sure if that was connected to the main issue or coincidental. I also think i might have a vacuum leak but not sure where. I can hear a hissing sound from inside the cab which makes me think I have a vacuum leak. I’m hoping that someone can help me pinpoint the issue. I’ll list the codes I’ve been getting along with the components I’ve replaced that I thought pertained to the issue but no luck. Here’s the codes:

P1400 - Differential Pressure Feedback EGR Circuit Low Input
P1351 - Ignition Diagnostic Monitor Input Circuit
P0443 - Evaporstive Emission System Control Valve Circuit

Heres what Ive replaced so far:

Distributor Cap and Rotor
Ignition Coil
Ignition Control Module
Throttle Position Sensor
Spark plugs and wires (nov 2018)

Also, I think I should note that I have a cracked passenger exhaust manifold as well as the metal tube that goes from the exhaust manifold to the egr valve. I’ve patched up those cracks with high heat exhaust epoxy as well as exhaust tape. I have even unplugged the egr vacuum solenoid and the canister purge valve and no change to how the engine runs.

I feel like I’m going in circles with all of this so any help y’all can give me is much appreciated!

 

P1400 Ford Meaning

1. The purpose of the Exhaust Gas Recirculation (EGR) system on your engine is to limit oxides of nitrogen (NOx) emissions. This is done by redirecting small amounts of exhaust gas back through the upper intake to get mixed in with the air/fuel charge. The resultant diluted air/fuel mixture (i.e., less oxygen per cubic foot) burns cooler and combustion chamber temperatures are reduced accordingly, thereby lowering NOx emissions.The Ford DPFE/EGR system is controlled by the Powertrain Control Module (PCM). The system employs an EGR Valve, an Electronic Vacuum Regulator (EVR), and a Delta Pressure Feedback EGR sensor (DPFE).

The DPFE Sensor measures EGR flow across an orifice located inside the special EGR Tube. The orifice is positioned between two hose ports coming off the tube which are connected to the DPFE sensor with special heat-resistant hoses. When the EGR Valve is open, a pressure differential is created across the orifice (intake manifold pressure vs. exhaust pressure). By design, this difference in pressure is measured by the DPFE sensor in terms of voltage. The DPFE voltage signal output to the PCM is directly proportional to the flow of exhaust gas entering the intake manifold.


2. The most common cause(s) of code P1351 – “Ignition Control Module Circuit Voltage”, are much the same across all applications that use this definition. However, some applications may have specific causes that do not occur on other applications, so always consult the manual for the application being worked on for detailed information on the causes that are most likely to produce code P1351 on that particular application. Below are some common causes of P1351-

• Damaged, burnt, shorted, disconnected, or corroded wiring and connectors
• Open circuits
• Defective/damaged Crankshaft Position Sensors
• Defective/damaged Camshaft Position Sensors (Where applicable)
• Abnormal system voltages caused by defects, malfunctions, or failures in the charging system
• Failed, or failing PCM. Note that replacing the PCM requires programming of the replacement

What are the symptoms of code P1351?

Apart from a stored trouble code and possibly an illuminated warning light, the typical symptoms of P1351 are largely make and model specific and much depends on the exact nature of the problem. Some applications might exhibit severe driveability issues, while on others the only immediately apparent symptom may be a no-start condition. However, some typical symptoms could include the following, but note that not all the symptoms listed here will always be present on all applications-

• No-start conditions may be present at all engine temperatures
• Engine may not start while it is hot
• In rare cases, the engine may start but shut off again after a few seconds
• Engine may not idle after reaching operating temperature.
• In some cases, the engine may develop serious misfires after reaching operating temperature
• If intermittent failures are present, the engine may shut off unexpectedly, or it may, or may not start in an unpredictable pattern

NOTE: This list of possible symptoms is neither complete, nor exhaustive. Always refer to the manual for the application being worked on for detailed information on the symptoms that are most likely to beset the vehicle when code P1351 is present.

How do you troubleshoot code P1351?

SPECIAL NOTES: In many cases, code P1351 is the direct result of using substandard aftermarket sensors, so one way to save a lot of diagnostic time is to check if the sensors on the application are OEM equipment as a first step in the diagnostic procedure. Many instances of this code can be resolved by replacing aftermarket sensors with OEM parts, but be aware that this does not always resolve the problem, and it might be necessary to work through the steps outlined here to diagnose and repair code P1351. END OF SPECIAL NOTES.

Step 1

Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.



NOTE: If any other codes are present along with P1351, these codes MUST be resolved in the order in which they were stored before attempting a diagnosis and repair of P1351, especially if any system voltage related codes are present.

Step 2

Assuming that no other codes are present, consult the manual to locate all relevant components, as well as the routing, color-coding, function, and location of all associated wiring to be sure that the correct circuits and components will be tested.



Perform a thorough visual inspection of all associated wiring and connectors, and look for damaged, burnt, shorted, disconnected, and corroded wiring and connectors. Make repairs as required, clear all codes, and rescan the system to see if the code returns.

Step 3

If no visible damage to wiring and connectors if found but the code persists, consult the manual to determine which type of crankshaft (and/or camshaft) sensors are fitted to the vehicle. If the sensors require an input voltage, consult the manual on the correct procedure to test the input voltage, and compare the obtained reading with the value stated in the manual.



If a deviation (a low voltage) is found, inspect all wiring between the sensor connector, the ignition switch, and the battery for poor connections, poor ground, or other issues that could affect continuity. Be aware though that this step involves checking and testing several individual circuits, so be sure to follow the instructions in the manual exactly to avoid causing short circuits that could damage other components and/or controllers. Note that on some applications, the PCM supplies the ground, so consult the manual on the correct procedure (KOER/KOEO) to establish the ground connection.



Compare all obtained readings with the values stated in the manual, and make repairs as required to ensure that all electrical values fall within specified values. Clear all codes after repairs are complete, and rescan the system to see if the code returns.



NOTE: Be sure to disconnect both the Ignition Control Module and the PCM from the wiring harness during resistance and /or continuity checks to avoid damage to either, or both controllers.

Step 4

Assuming that the charging system checks out OK and that the battery is not damaged or over charged on older applications, high input, or reference voltages in the Crankshaft Position Sensor circuit is almost always caused by a short circuit to the battery positive. However, this condition will almost certainly be indicated by a code other than P1351, so check again for the presence of other codes, and resolve these codes before proceeding to the next step.

Step 5

If a short circuit to battery positive is suspected, inspect all associated wiring/connectors, and repair, or replace wiring/connectors as required. Clear all codes after repairs are complete, and rescan the system to see if the code, or any other codes, returns.

NOTE: Since the Crankshaft -, and/or Camshaft Position sensors form part of the circuit, these sensors must be tested as well. Consult the manual on the correct procedure to test the sensors, and replace all sensors that do not conform to the manufacturer’s specifications.

Step 6

If the sensors do not require an input voltage, carefully check the air gap between the sensor and the reluctor wheel on the crankshaft pulley. In some cases, it is possible for the sensor retaining bolts to work themselves loose, which can cause the air gap to increase to the point where the sensor does not work.

Reset the air gap to the specified clearance, clear all codes, and rescan the system to see if the code returns. If the code persists, remove the sensor from the engine and inspect it for signs of impact damage, or evidence that it might have rubbed against the reluctor wheel. Replace the sensor if signs of mechanical damage are found, and rescan the system after the replacement to see if the code returns.

If the sensor is not damaged in any way but the code persists, consult the manual on the correct procedure to test the sensor, and replace it if it does not conform to the manufacturer’s specifications.

Step 7

If the code persists despite several repair attempts, it is likely that an intermittent fault is present, which can sometimes be found by “wiggling” all connectors and wiring while the voltage in a circuit is being monitored with a multimeter. If there is an intermittent fault present, the reading displayed on the multimeter will often change in direct response to the “wiggle” test, but be aware that some intermittent breaks, short circuits, or losses of ground connectivity in wiring do not always respond to this test.

Therefore, the better option if an intermittent fault is suspected is to refer the vehicle for professional diagnosis and repair, since the diagnosis and repair need to be definitive and reliable.

Step 8

The generic diagnostic/repair steps up to this point will usually resolve nine out of every ten instances of code P1351, but in some cases, the code involves abnormal voltages between the PCM and the Ignition Control Module.

The diagnostic steps required to diagnose this condition are make and model specific, but unless a wiring problem between the PCM and the Ignition Control Module is identified, the only remedy for this condition involves replacement of the PCM. Take note that replacing a PCM requires programming of the replacement PCM, which is a procedure best left to professional technicians who have access to the required equipment and software.

Also, note that testing for PCM faults require testing pins and terminals on the PCM itself, which requires a pin-out chart for that specific application and PCM. DO NOT attempt to test ANY circuit on a PCM if a pin-out chart and repair manual is not available. Doing so could not only destroy the PCM, but several other controllers as well. If a defective PCM is suspected, the better option is to refer the vehicle for professional diagnosis and repair

3.

P0443 code definition

Evaporative Emission Control System Purge Control Valve Circuit Malfunction

What the P0443 code means

P0443 is an OBD-II generic code that the engine control module (ECM) has detected a malfunction with the purge control valve or its control circuit. This could mean an open or short in the valve or circuit.

What causes the P0443 code?

• The ECM has commanded the purge control valve to open and detected either an incomplete open circuit or a short in the circuit.
  
• The cause of code P0443 can be a purge control valve internal open circuit or the connector is corroded causing loss of contact with the valve.
  
• The code can also be set if the wiring to the valve is damaged between the ECM and the purge valve causing an open circuit if the wire is cut or a short if the wire is shorted to ground or a power source.
  

What are the symptoms of the P0443 code?

• The Check Engine Light will be illuminated and the code is set in ECM memory.
  
• You may notice a slight drop in fuel mileage if the vapor system is not working.
  

How does a mechanic diagnose the P0443 code?

• Scans codes and documents the code in the ECM, views the freeze frame data see when the fault happened
  
• Inspects the entire vapor purge valve wiring and system to include the purge valve connector for corrosion, damaged or loose connection or wires
  
• Checks the purge valve vent for any blockage from dirt, debris, or spider webs
  
• Performs a smoke leakage test on the fuel vapor system to try and locate the cause of the vapor leak using the test vapor port
  
• Checks the purge control valve for proper resistance of valve and then check operation of valve using the ECM to control the valve
  

Common mistakes when diagnosing the P0443 code

• Not checking and assuming the purge control valve is defective without doing a thorough diagnostics of the complete system to later find the wiring is broken or cut
  
• Not verifying the failure and replacing parts that may or may not be the problem
  

How serious is the P0443 code?

• Code P0443 causes the check engine light to go on and this alone will cause a failed emission test.
  
• The code means the fuel vapor system control valve is defective or the circuit to it is not making the connection to the valve so the ECM lost control to the valve.
  
• The vapor recovery and reuse system if not working correctly can cause a loss of fuel mileage.
  

What repairs can fix the P0443 code?

• Testing and replacing the purge control valve
• Repairing the damaged wiring to the purge control valve and secure from getting damaged again
• Replacing the purge vent valve

Additional comments for consideration regarding the P0443 code

Code P0443 is a pretty common code that vehicles come in with today that causes the check engine light to come on. The most common cause is the fuel cap was accidently left off or not tightened securely after getting fuel. For this code the most common failure is the purge control valve has an internal open circuit or the vent valve will not hold in the vapors.



Sandy