testing egr components
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testing egr components
Hi.
I am trying to diagnose egr code 332 (egr valve opening not detected). '88 460.
The EVR gets grounded through pin 33 of the ecu. If I put a voltmeter between the battery negative and pin 33, I get alternator voltage, which makes sense. But if I connect the voltmeter between the battery positive and pin 33, I still get about 1 volt. This spikes to about 5 or so if I jam the throttle, which I guess is the EVR opening. Does this mean I have a short to ground in the supply wire to the EVR? Thanks.
I am trying to diagnose egr code 332 (egr valve opening not detected). '88 460.
The EVR gets grounded through pin 33 of the ecu. If I put a voltmeter between the battery negative and pin 33, I get alternator voltage, which makes sense. But if I connect the voltmeter between the battery positive and pin 33, I still get about 1 volt. This spikes to about 5 or so if I jam the throttle, which I guess is the EVR opening. Does this mean I have a short to ground in the supply wire to the EVR? Thanks.
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Well I got some strange results. According to the site (Ford Fuel Injection » EGR Valve Position sensor (EVP)) as the EGR valve opens, the VREF signal decreases while the EVP signal increases. As I manually pumped the valve open to 8" Hg, the VREF signal decreased from 14 to about 7 volts, but the EVP signal also decreased from 8.5 to about 7. I'm not so sure the sensor is at fault though. Could this have anything to do with the stray voltage I mentioned earlier? I know the EVR isn't powered by the same circuit but just thought it might have something to do with it. Thanks.
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What are you using for a ground reference? VREF should never be much more or less than 5.00 VDC (+/- 0.2 VDC).
The EVR is controlled by the PCM. It is supplied with battery voltage (plus alternator voltage when the engine is running). The ground is modulated off and on by the PCM. You cannot accurately measure across the EVR with a DVM. It would require an oscilloscope. You can measure the supply voltage, but beyond that it takes a better measurement tool. One test you can do is momentarily ground the negative side (Pin 33) of the EVR. If the EVR opens, you know the circuit is good.
The EVR is controlled by the PCM. It is supplied with battery voltage (plus alternator voltage when the engine is running). The ground is modulated off and on by the PCM. You cannot accurately measure across the EVR with a DVM. It would require an oscilloscope. You can measure the supply voltage, but beyond that it takes a better measurement tool. One test you can do is momentarily ground the negative side (Pin 33) of the EVR. If the EVR opens, you know the circuit is good.
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What are you using for a ground reference? VREF should never be much more or less than 5.00 VDC (+/- 0.2 VDC).
The EVR is controlled by the PCM. It is supplied with battery voltage (plus alternator voltage when the engine is running). The ground is modulated off and on by the PCM. You cannot accurately measure across the EVR with a DVM. It would require an oscilloscope. You can measure the supply voltage, but beyond that it takes a better measurement tool. One test you can do is momentarily ground the negative side (Pin 33) of the EVR. If the EVR opens, you know the circuit is good.
The EVR is controlled by the PCM. It is supplied with battery voltage (plus alternator voltage when the engine is running). The ground is modulated off and on by the PCM. You cannot accurately measure across the EVR with a DVM. It would require an oscilloscope. You can measure the supply voltage, but beyond that it takes a better measurement tool. One test you can do is momentarily ground the negative side (Pin 33) of the EVR. If the EVR opens, you know the circuit is good.
As for the EVR test, that's what I was posting about above. It's working fine.
Thanks.
edit: I thought you were talking about the EVP when you said I need an oscilloscope. So I guess what you're saying is that the ECU is quickly energizing/denergizing the EVR to apply a certain amount of vacuum to the valve, right? In any case the EVR seems to be working fine, it's the EVP I'm trying to diagnose.
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Not sure what you mean by ground reference, but I'm just using a regular DVM hooked to either the battery + or - on one side with the other backprobing the wire. If that doesn't work I guess I need an oscilloscope?
As for the EVR test, that's what I was posting about above. It's working fine.
Thanks.
edit: I thought you were talking about the EVP when you said I need an oscilloscope. So I guess what you're saying is that the ECU is quickly energizing/denergizing the EVR to apply a certain amount of vacuum to the valve, right? In any case the EVR seems to be working fine, it's the EVP I'm trying to diagnose.
As for the EVR test, that's what I was posting about above. It's working fine.
Thanks.
edit: I thought you were talking about the EVP when you said I need an oscilloscope. So I guess what you're saying is that the ECU is quickly energizing/denergizing the EVR to apply a certain amount of vacuum to the valve, right? In any case the EVR seems to be working fine, it's the EVP I'm trying to diagnose.
The EVP signal is affected by the EVR operation. Your test of applying vacuum to the EGR valve which also changes the EVP signal output is a valid test. Your results are what I am questioning. The VREF signal should not change. The EVP signal output is what changes.
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Ok thanks.
I did the test again. Now what I'm getting is at idle the EVP and SIG RTN have alternator voltage which decreases from ~14 to 12.5 as the valve opens, while the VREF wire drops from 9.5 to 7.5 or so. I'm guessing the EVP is toast? That page does mention that the VREF signal should decrease though. Thanks.
I did the test again. Now what I'm getting is at idle the EVP and SIG RTN have alternator voltage which decreases from ~14 to 12.5 as the valve opens, while the VREF wire drops from 9.5 to 7.5 or so. I'm guessing the EVP is toast? That page does mention that the VREF signal should decrease though. Thanks.
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You have something seriously wrong. VREF should not change....ever. The EVP output signal should be between ~0.24 to 0.67 VDC with the EGR closed. The EVP signal will increase to the 3.9 to 4.4 VDC range depending on what color EVP you have. The voltages you are getting are way out of whack. I wonder if the readings you are getting is caused by an open Signal Return wire?
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nope, not a short. An open circuit. You will get very odd readings with an open wire and a high impedance DVM. I won a few rounds of beer when a partner I was working with was driving himself insane troubleshooting an electronics circuit. He was getting very strange readings, he worked on it for 2 days before he threw his hands up and left. Turns out the signal supply wire was open, but it measured 120V with the DVM. It was a phantom voltage induced by the other wires in the bundle.
It could be an open VREF or Signal Return check both of them.
It could be an open VREF or Signal Return check both of them.
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Well I performed continuity tests on the BK/W SIG RTN wire (after unplugging everything and removing the conduit for a better view). I found that there is continuity between the sensor and pin 46 of the ECU connector, however, the two adjacent pins and the one directly below it also had partial continuity, with 500-800 ohms. I have no idea if this is significant, and no other pin behaved this way. I also tested the same wire where it splices off to the VIP, and that had continuity.
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Your '88 has different wire colors than the 1992 and up EVTM manuals I have so wire colors are not going to jive with my info. All I know is Signal return is common to pin 46, VREF is pin 26 and the EVP signal goes into pin 27. I still suspect an issue with an open wire. Your tests lead me to think Signal Return is good, but VREF is suspect.
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I decided to test the EVP off the truck. I put a 12V battery with the + on the SIG RTN, the - on the VREF, and hooked my voltmeter between the EVP and battery -. I think this is right? Anyway, I got battery voltage at closed, and it moved smoothly to .39 volts at fully open. Is that right?
Edit: I forgot you mentioned VREF is supposed to be at 5 volts. Doesn't that mean SIG RTN would also be at 5 volts?
Edit: I forgot you mentioned VREF is supposed to be at 5 volts. Doesn't that mean SIG RTN would also be at 5 volts?