egr circuit or vref circuitry could be compromised in pcm

Whats became of this

suppose it could take a pcm out
were any fuse blown ?

Vref still at 5 volts?

 

Original engine harness and this is the 2nd replacement EGR from Apple Ford. The original EGR was stuck in a partially open position and wouldn't move when commanded. I was able to clean it up, but it would still stick open when it was commanded fully open. The replacement EGR valve worked for 2 days, then got stuck open. Ford replaced that one with the current one I have.

I haven't done an end-to-end continuity test or an isolation test on the harness, just visually inspected. This is my next move, to disconnect both the PCM and EGR valve and measure continuity and perform isolation testing between conductors. I have a high pot tester to measure insulation resistance to detect potential rub throughs between conductor-conductor and conductor to chassis. I did measure vref with the DVOM and it was 4.98V.

 

I extracted the pin from the connector and slid heat shrink over the exposed wire and placed conduit over the harness. Vref is at 4.98V. No fuse blown.

 

No check engine light ever came on, but I did have a P404 code several times with the original EGR valve that had the stuck pintle. When the EGR is being commanded, I will try the wiggle test at the connector and flex the harness on it's path back to the PCM.

 

Sensor spec sheet
It’s important that you must meet the operating conditions at top left of this spec sheet when you take sensor values

check values when it’s running rough maybe something will stand out post values for low idle and high idle2500 rpm

 

Just curious, are you watching the EGR desired and EGR actual position pids, and are they in agreement when acting up? At least I think both those pids are available.

 

Sorry for late response. I'll post/attach a few things that I have that might apply.

Exhaust Gas Recirculation Monitor:

EGR System and Comprehensive Component Monitors:

The Delta Pressure Exhaust Gas Recirculation (EGR) System is a closed loop EGR Valve Position control system.
It utilizes an exhaust manifold pressure sensor, an intake manifold pressure sensor and a speed density estimate of total mass flow and derives a desired EGR Valve position based on a desired EGR flow percentage.

The EGR Monitor is a series of electrical tests and functional tests that monitor various aspects of EGR system operation.

When normal EGR rates are being commanded and when the engine enters into either one of two specified operating ranges, a flow check is performed. The operating ranges are defined to insure an adequate amount of EGR is being requested to allow for an accurate estimate of the EGR flow percentage. At this point EGR flow is estimated based on the difference between the Mass Air Flow (MAF) sensor reading and the total mass flow calculated by the speed density calculation. The estimated EGR flow is then compared to the expected EGR flow to determine if there is insufficient or excessive flow.

Exhaust Gas Recirculation Position Sensor (EGRP):

DTCs:Monitor execution: Continuous (8ms)
Monitor Sequence: None
Sensors OK: Not Applicable
Typical Monitoring Duration Less than 1 second

Typical Exhaust Gas Recirculation Position Sensor Entry Conditions:
No entry conditions.

Typical Exhaust Gas Recirculation Position Sensor Check Malfunction Thresholds:
Voltage less than 0.30 volts for P0405 and voltage greater than 4.90 volts for P0406

Exhaust Gas Recirculation Valve Actuator (EGRAM) Monitor Operation:
DTCsMonitor execution: Continuous
Monitor Sequence: None
Sensors OK: Not Applicable
Monitoring Duration: Less than 1 second

Typical Exhaust Gas Recirculation Valve Actuator Monitor Entry Conditions:
No Entry Conditions

Typical Exhaust Gas Recirculation Valve Actuator Monitor Malfunction Thresholds:
Actuator driver status indicates open/short

Exhaust Gas Recirculation (EGR) Valve:
DTCs:Monitor execution: Continuous (8ms)
Monitor Sequence: None
Sensors OK: Exhaust Gas Recirculation Position (EGRP)
Typical Monitoring Duration: Greater than 10 seconds.

Typical Exhaust Gas Recirculation (EGR) Valve Entry Conditions:
Engine Running: (mode = 2)

Typical Exhaust Gas Recirculation (EGR) Valve Thresholds:
+/- 0.10, out of a total working range from 0 to 1, error from the commanded position to the actual position.

Exhaust Gas Recirculation (EGR) Monitor Operation:
DTCsMonitor execution: Continuous (8ms)
Monitor Sequence: None
Sensors OK:Monitoring Duration: 15 seconds cumulative

Typical Exhaust Gas Recirculation (EGR) Monitor Entry Conditions:
Exhaust Gas Recirculation is commanded greater than 10% open and one of the following conditions exist.
Condition 1: Engine speed (N) 1000-1800 RPM and fueling desired (MFDES) 10-16 mg/stroke.
Condition 2: Engine speed (N) 1800-2500 RPM and fueling desired (MFDES) 12-29 mg/stroke.

Typical EGR Monitor Malfunction Thresholds:
Limits based on engine speed and load.

 

Wire diagram

 

Thanks for the info fellas, looks like I'll be busy this weekend making use of it. I'll let you know what I find either way. Starting with wiring, then collecting run data.