Do you have to calibrate the EGR position sensor?

[Corrie06]

When replacing the position sensor on the EGR valve, does it need to be calibrated somehow? I had a DTC for EGR valve insufficient flow so, after some troubleshooting, I replaced the position sensor. Immediately after replacing the sensor I got EGR valve exissive flow! I cleared the code and it came back. When I replaced the sensor I did not remove the valve--only the sensor--and I've ensured all the hoses and wires are hooked up. Can someone tell me what went wrong and what I should do to fix it? I appreciate any help. :

 

[2000StreetRod]

PFE System

I believe the 1996 5.0L V8 uses a Pressure Feedback EGR (PFE) instead of the later Differential Pressure Feedback EGR (DPFE). By "position sensor" are you referring to the pressure feedback sensor? Your EGR valve could be sticking. I suggest that you remove the EGR valve and clean the inlet and outlet ports with a wire brush or scraper. Do not use any solvents!

The EGR valve should be closed at idle and wide open throttle. It should be open intermittently (based on a duty cycle controlled by the PCM) when the throttle position and MAF sensors are midrange and the engine is warm. I'm not aware of any calibration procedure for the EGR other than making sure that the TPS and MAFS outputs are correct.

 

[Corrie06]

Correct, I don't have the DPFE. You may call it "pressure feedback sensor" but Oreilly's calls it EGR position sensor. It's the sensor mounted on the EGR valve. I think we're talking about the same thing.

This started with P0401 EGR flow insufficient. A few weeks ago I removed the EGR valve to clean and test it. It holds vacuum fine. I reinstalled it with a new gasket and tested that it would hold vacuum again and it did. I still had the P0401 code at this point. I replaced the sensor and cleared the code. The CEL came back on immediately with P0402 EGR flow excessive. I made sure all hoses and wires were hooked back up and all I did was replace the sensor so I'm not sure what would have been to done get the opposite code...

 

[2000StreetRod]

Sonic EGR System

Upon further research, I learned the following:

The Sonic EGR system is a closed loop EGR control system that consists of a vacuum-operated EGR valve with an EGR Valve Position (EVP) Sensor for feedback. The EGR valve is regulated by a duty-cycled EGR Vacuum Regulator solenoid. The PCM uses the EGR Valve Position Sensor for feedback control by measuring the position of the EGR valve pintle. On a Sonic EGR valve, the valve is designed such that the position of the EGR valve pintle is proportional to the amount of EGR flow, independent of the downstream manifold pressure. The PCM calculates the desired EGR rate and adjusts the duty cycle to the EVR to obtain the desired EGR rate by monitoring the EGR Valve Position signal.

As the EGR valve opens, the EGR Valve Position signal voltage increases. Normal EVP sensor voltage at idle (closed EGR valve) is between 0.24 and 0.67 volts.) The EGR Valve position signal only detects EGR valve pintle position. EGR flow is inferred from the pintle position. Actual blockage of EGR flow cannot be detected using the EVP signal. Therefore, cleaning the ports should have no impact on test results.

An electrical test of the EVP sensor is continuously performed. Did you have DTC P1400, P1401 or P1409 displayed? If not then the PCM read the EVP sensor voltage to be within range (4.81 to 0.048 volts).

After the vehicle has warmed up and normal EGR rates are being commanded by the PCM, the low flow check and a stuck open at idle check is performed. Since the Sonic EGR system uses EGR valve position for feedback, actual blockage in the EGR tubes and passages cannot be detected.

If the control system cannot open the EGR valve to the desired position, a P0401 will be set. The test is run if there is sufficient vacuum to open the valve, and the requested EVR dutycycle is high (>70%). If EVP sensor voltage: < 0.78 volts when commanded open then P0401 is set.

If the EGR valve position indicates that the EGR valve is stuck open at idle when commanded closed, a P0402 is set.(EVP sensor voltage: > 0.72 volts)

Since the sensor has been replaced, I suspect that there is now an electrical connection or wiring problem. Check the electrical connection and for broken or shorted wires.

 

[Corrie06]

Thanks for the info. Since I cleared the code the first time it does not come back immediately, but has come back. I cleard it this morning and drove 25 miles to work and it never came on. When I get home tonight, I'll check the connection and wires again and I'll check that the valve is not stuck open. I'll also see if I can find some t-pins and read the voltage at idle. Do you know which wires are which? If memory serves, there is a brown, gray, and orange.

 

[2000StreetRod]

Wire colors

. . . I'll also see if I can find some t-pins and read the voltage at idle. Do you know which wires are which? If memory serves, there is a brown, gray, and orange.

From the wiring diagram it looks like brown/white is the reference voltage, orange/yellow is the variable resistance (voltage) and gray/red is signal return. The voltage between brown/white (+) and gray/red (-) should be constant and between 4.0 and 6.0 volts. The voltage between orange/yellow (+) and gray/red (-) should vary according to engine conditions.

You may also want to check the EGR vacuum regulator solenoid wiring. According to my Haynes Repair Manual the resistance with the connector removed should be 20 to 70 ohms. If the regulator isn't working correctly then the sensor will report what appears to be an incorrect value.

 

[Corrie06]

I checked the resistance on the solenoid. It was 34.6 Ohms which seems to be within spec. So the solenoid is good?

I couldn't find my t-pins so I guess I'll have to get some more to test the voltage on the postition sensor. I'll report back when I have the results of the test.

 

[Turdle]

Is the position sensor not vacuum "powered"

A small vacuum leak in the vacuum solenoid diaphragm would not show on a resistance check.

 

[2000StreetRod]

Solenoid resistance

I checked the resistance on the solenoid. It was 34.6 Ohms which seems to be within spec. So the solenoid is good?

I couldn't find my t-pins so I guess I'll have to get some more to test the voltage on the postition sensor. I'll report back when I have the results of the test.

Haynes says the voltage to the solenoid with the connector disconnected and the ignition On but engine not running should be battery voltage.

Is the position sensor not vacuum "powered"

A small vacuum leak in the vacuum solenoid diaphragm would not show on a resistance check.

The position sensor reports the position of the EGR valve which is vacuum controlled by the EGR vacuum regulator. The vacuum regulator is controlled by the PCM via an electrical solenoid.

 

[Corrie06]

I checked the voltage on the sensor with engine running. It was 4.20 volts and EGR valve was closed.

 

[2000StreetRod]

Wrong voltage

I checked the voltage on the sensor with engine running. It was 4.20 volts and EGR valve was closed.

When the engine is idling, the EGR valve should be closed - which it is. However, the PFE voltage reading should be less than 0.72 volts. Either your FPE is bad or there is a problem with the vacuum line to it. I'd suspect the vacuum line since you have recently replaced the PFE. Make sure that the vacuum line is not broken or loose allowing atmospheric pressure to the PFE. Make sure that the vacuum line is not kinked or clogged preventing vacuum from passing to the PFE.

 

[2000StreetRod]

brown/white or orange/yellow?

I checked the voltage on the sensor with engine running. It was 4.20 volts and EGR valve was closed.

Which wire to gray/red was 4.2 volts - brown/white or orange/yellow?

 

[Corrie06]

I must have probed the wrong wire last time because I double-checked it tonight. The voltage across the gray and orange wires is about 0.79 volts with engine idling.

The vacuum tube is clean and free from obstruction, but just to be safe, I'll replace it and see what happens.

 

[2000StreetRod]

Just barely out of tolerance

I must have probed the wrong wire last time because I double-checked it tonight. The voltage across the gray and orange wires is about 0.79 volts with engine idling.

The vacuum tube is clean and free from obstruction, but just to be safe, I'll replace it and see what happens.

Sorry about taking so long to get back to you. I've been busy!

That sounds much better! 0.79 volts is an indication the valve is actually closed but the voltage slightly exceeds the limit of 0.72 volts causing the PCM to set the DTC. I suspect that your EGR system is working fine. All you need to do is get the closed position voltage lower so the DTC doesn't get set. Try disconnecting and reconnecting the connector a couple times as a way to clean the connector pins. I don't know if the PCM has a "learn" capability for the EGR system. In case it does, try disconnecting and then reconnecting the negative battery terminal after 10 minutes to erase the Keep Alive Memory.

 

[Corrie06]

Sorry about taking so long to get back to you. I've been busy!

No problem. I've been busy too and haven't had the time to commit to this that I'd like.

This weekend I replaced the small hose between the solenoid and valve with no change, but I didn't expect there to be any.

I also loosened the position sensor as much as I could while still being able to suck on the hose and hold vacuum. The voltage at that point was .66 (yay)! Unfortunately, it must be too loose because I got P0401 insufficient flow on my way to work this morning. I'll go home and tighten it a bit more and see if that helps the situation. I'll keep you posted.

 

[2000StreetRod]

check the return

Here's another idea. Measure the voltage between the gray/red wire and the negative battery terminal. That will reflect the conductivity of the sensor ground. The TPS, IAT, ECT, and EGR valve position sensors all tie together to a central return which should be grounded. See if you can follow any of the gray/red wires to a ground and then make sure it is a good connection.

 

[2000StreetRod]

Sensor return not grounded

I checked the wiring diagram again and it turns out that the sensor returns are all tied together but not grounded. They just return to the PCM. That's why I couldn't find the location of the tie point on the wiring diagram. The only way to find it is to trace the wires.

 

[Corrie06]

I tightened the sensor again (to .69 volts) but still got the insufficient flow code. I guess I'll try to trace the ground wire now and see if there are any problems with it.