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EFIE chip troubleshooting
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jared Offline
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Post: #1
EFIE chip troubleshooting
I purchased an EFIE chip and installed it on my 89 ford ranger, and I am experiencing problems with the check engine light coming on. So I figured it was to lean and turned it down but that din't help, and I turned the led/switch off to get back the stock setting but the light was still on. So I bypassed the chip and wired it back up and the check engine never came back on. So what is wrong with the EFIE chip? Jared
09-18-2007 05:09 PM
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mike Offline
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Post: #2
RE: EFIE chip troubleshooting
Ok Jared thanks for the information. Yes, you have connected the EFIE correctly provided the information you received from the manual is correct. Let's do a couple of tests:
  1. Test the voltage between the red and black probe jacks on the EFIE. You should see a voltage of .250 volt, or lower since you earlier backed off the set point. However, when you turn on the truck's accessory key switch, the voltage will start low, and slowly come up to it's set point. It'll be pretty close after a minute, and will be quite steady after 3 minutes.
  2. Start the truck and re-read the voltage. It should rise some as the voltage of the system will be a couple of volts higher with the alternator running. But should still be in the same range, less than .25 volt.
  3. Now test between the black probe jack and ground, with the engine running. This will show you the voltage that is coming from the oxygen sensor's signal wire. It should be oscillating around quickly enough that you can't actually get a reading, but all the numbers you see should be between 0 and 1 volt.


The first 2 steps will tell us if the EFIE is working properly, and will verify it's setting. The third step will tell us that we have connected to the correct wire on the oxygen sensor and that the oxygen sensor is working properly.

I"m going to assume that you're dead certain as to which side of the cut sensor wire goes to the sensor and which goes to the ECU. It may be infinitely obvious in the case of your truck, but sometimes it's hard to tell which wire goes where. If that's the case, verify for sure that those wires aren't reversed by unplugging the EFIE, starting the truck and measure between the plug terminal connected to the green wire and ground. You should see that oscillating voltage between 0 and 1 volt. If it's connected to the ECU, it'll be 0 volts.

If all 3 of these steps check out OK, then we're going to go ahead and set the EFIE to ABOVE .250 volts. Note that a lower voltage to the ECU means the mix is too lean to the computer, and a higher voltage means a richer mix. You have 2 fuel savers there, and the vapor system, in particular, can increase your fuel burn efficiency significantly, and cause extra oxygen to be in the exhaust. This makes the computer think the fuel/air is too lean, and it'll dump extra gas into the cylinders, and it's also complaining, because despite dumping extra gas it sees what it thinks is a too lean condition continuing. We need to raise the voltage it sees so it thinks the air/fuel mix is correct and quits dumping in extra, un-needed gas. So let's try .300, .350, .400 and .450 volts on the EFIE. At some point the check engine light should go out (you probably need to reset the ECU each time you test).

Please let me know how that goes for you.

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09-19-2007 05:21 AM
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jared Offline
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Post: #3
RE: EFIE chip troubleshooting
I did some more test on my ranger and found that there is no voltage change on the signal wire coming or going to the ECU when the chip is installed. And with the origonal oxygen/ECU wire hooked up there is a voltage alternating between 13.5v and 14.5v when I test it with the voltmeter. Is this the right signal, or is my oxygen sensor bad or what? Jared
09-19-2007 10:07 AM
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mike Offline
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RE: EFIE chip troubleshooting
My first guess is that you have a heater supply wire. Oxygen sensors are often heated, with a coil and battery voltage to bring them up to operational temperature quickly. They don't read right until they are hot. Some sensors don't have heaters and just wait until the engine gets hot enough to provide the heat for proper operation. Any sensor that has more than 2 wires must be a heated sensor.

If you actually have the signal wire, then for sure the sensor is shot, because the signal should oscillate in the range of 0 to 1 volt. Note, that the readings will only be correct after the sensor has heated up. So make sure the engine has been running a bit before deciding that. You can leave the sensor disconnected from the ECU and run the engine without harming it. I don't think 12 volts will harm the ECU either, but I wouldn't take the chance. The sensor signal is designed to be 1 volt max.

If you can access the oxygen sensor, unplug the wiring harness and (with AC switch turned on), test for 12 volts. That wire will be a heater circuit. Then for the other 2 wires, test for continuity to ground. That one will be (take a wild guess), ground. The remaining wire will be the signal wire. Test this wire for continuity with what you think is the signal wire up by the ECU, to make sure you really have the signal wire. If you for sure have the signal wire, then yes the oxygen sensor is shot. I find this unlikely though because (if I understand correctly) the check engine light wasn't on before you installed your fuel savers and EFIE, correct?

If you don't have the correct signal wire (which I think is most likely) then I question the wiring diagram you got from the parts house. You might want to invest in a wiring diagram from ahdol.com. I have a Chilton's manual for my car, and found that it had a wrong color for one of my sensor wires, whereas the diagram I got from ahdol.com had the correct color. For $11.00 you can get all the wiring diagrams for your truck, and it's less than $5 for just the one you need. It should be called the Engine Performance Circuit Diagram, which gives all of the devices that connect to the ECU.

Please check these things out, and let me know what you find.

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09-19-2007 12:01 PM
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jared Offline
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Post: #5
RE: EFIE chip troubleshooting
I have been trying to figure out why my oxygen sensor signal wire is producing 13.?v when the engine is runing with the wire hooked up to the ECU. This signal wire is not one of the other two heater wires because tested them right at the plug and viewed them on the diagram I purchased. The last few test were not concerning the EFIE chip because it is wired back up stock. What's odd is the fact that the oxygen sensor new so it can't pluged up, grounded, or malfunctioning. Is it possible the ECU is goofy, because with the signal wire disconnected and the side going to the ECU has a reading of 6.v or more with the engine off. The last few days I have been experiencing the engine light coming on without the EFIE. So it's kind of strange as to what's going on. Jared
09-21-2007 02:52 PM
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mike Offline
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RE: EFIE chip troubleshooting
I'm not sure I understood everything. Correct me if I'm wrong on any of these points:
  • You've definitely, definitely established the heater circuit (which puts 13 volts TO the oxygen sensor.
  • You've definitely established ground, and tested it for continuity to the frame of the truck or some such.
  • You've measured the ECU wire that the oxygen sensor signal wire ordinarily connects to and read 6 volts. This while the oxygen sensor was disconnected.
  • You have a new oxygen sensor.
I'm not too worried about this last point. When the engine is off, there could be a capacitor in there that only has a chance to discharge when the circuit is on, or when it's hooked up to a sensor.

Here's some questions for you:
  1. Is the new oxygen sensor new today? or did you get this before you started the project. Is it known to be good? Were you driving the car with it, with the engine light not on, for a period of time?
  2. Have you definitely established the oxygen sensor signal wire up by the ECU such that you could bet your life that it's the correct wire? Any doubt about this?
  3. What is the voltage reading of the signal wire to ground, with the engine running and while it's disconnected from the ECU? Reading the output from the sensor only, with the ECU out of circuit? Ensure the truck is running a few minutes before taking this reading to ensure the sensor is warmed up.

I really want to isolate the oxygen sensor from the ECU and test it's output vs ground. I'm suspicious that despite being new, it doesn't work.

There's really very few things that could be wrong. It's either the oxygen sensor doesn't work, even though new, the wires are wrong (as in you somehow got them mixed up during all this), or the ECU is shot, possibly zapped by the 13 volts. Just so you know, I doubt it's the latter because I had a bad sensor one time and it was producing voltage up to 12 or 13 volts, and it didn't damage my ECU. Really it would take a pretty bad design to have the ECU die from 13 volts on that line since a bad sensor puts out over-voltage.

Let me know on these. I'm sorry if some of these questions seem dumb. If I was there and could see what you see, I might not ask some of them. But humor me, and answer them, and we'll get this thing figured out.

Mike

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(This post was last modified: 09-21-2007 03:26 PM by mike.)
09-21-2007 03:25 PM
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jared Offline
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Post: #7
RE: EFIE chip troubleshooting
I have figured out some things on my ranger. I am now driving my truck with the EFIE reconnected to the oxygen/ECU signal wire. The oxygen sensor is working properly, and I cut into the right signal wire but when I tested the sensors signal I had the other meter probe on a positve charge instead of being on ground and I got a false reading. The check engine light is off now but it was on earlier witch may have been the the other oxygen sensor or an incorrect EFIE setting, but I have it at 375millivolt now. It is allmost impossible to make fuel savers work as long as the oxygen sensor and ECU are doing there job, so it's ether use a carburator or get an EFIE. I will let you know if I run into any more trouble thanks! Jared
09-23-2007 07:56 PM
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mike Offline
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RE: EFIE chip troubleshooting
That's great news Jared. I'll be here if you need anything.

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09-23-2007 07:59 PM
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jared Offline
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Post: #9
RE: EFIE chip troubleshooting
Should the voltage offset stay the same when I adjust my EFIE, or will it vary throughout the hours of driving. If I had it at 250mv offset with engine running what should it be ten minets later? Jared
10-29-2007 09:00 PM
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mike Offline
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Post: #10
RE: EFIE chip troubleshooting
The voltage offset will be slightly higher if the engine is running as compared to if it's off, and the EFIE is getting battery voltage only. This is because the alternator puts a slightly higher voltage on the "12 volt" line.

The EFIE has a built in delay. It takes about 5 minutes before it reaches it's full voltage. This is by design, but can be a bit of a pain when setting the EFIE as you have to wait for it to acheive it's full voltage. However, it doesn't change after that. If you wait a full 5 minutes, with the engine running, that will be it's operating voltage from there on out. It doesn't change further as you drive.

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10-29-2007 09:19 PM
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