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  #61  
Old May 8th, 2011, 14:03
CoastieCJ CoastieCJ is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
I ran direct ground wires directly from the negative post to both sides of my TPS sensor on my 87 Renix, after fixing all the main system grounds. Made a big difference.
I replaced the main ground wire to the pcm with one direct to the battery, but no difference to the running issue(getting a good .01 Ohm connection though at the O2 sensor). The sensor ground is now showing about 1ohm with the key off, but it jumps to 35ohms when the key is on. I know the PCM "filters" the sensor ground, but this seems high. Any thoughts?

Last edited by CoastieCJ; May 8th, 2011 at 14:26.
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  #62  
Old May 8th, 2011, 18:32
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Re: Testing Jeep O2, Oxygen sensors

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Originally Posted by CoastieCJ View Post
I replaced the main ground wire to the pcm with one direct to the battery, but no difference to the running issue(getting a good .01 Ohm connection though at the O2 sensor). The sensor ground is now showing about 1ohm with the key off, but it jumps to 35ohms when the key is on. I know the PCM "filters" the sensor ground, but this seems high. Any thoughts?
Repeat the test that gave you 35 ohms, but use the DC volts scale, then the AC volts, and let me know what it reads under the same conditions. You said "with key on", but was the engine running or not?

But, frankly I do not have enough hands on experience with the HO, O2 sensor -ECU wiring to be sure, but sounds like it might be an ECU connection, external or internal. On the other hand, somebody posted here recently about how the HO-ECU sends a signal to or through the O2 sensor? But I forget the details, as it sounded kinda screwy to me to begin with. It was something from an XJ manual on the later jeeps I think?

When in doubt, find an XJ buddy and test the same wires on his!!!!
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  #63  
Old March 17th, 2012, 22:55
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Muad'Dib Muad'Dib is offline
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Re: Testing Jeep O2, Oxygen sensors

Ive been hunting down an issue with my RENIX (90) and i dont have +12v at the orange wire wire with the key on. Only with engine running do i get +12v. Ive tested directly at the relay, and on the diagnostic connector (there is a pin for the 02 heater there) and i dont get the 12v.
Is this an ECU issue or normal? I have come across a few threads that mentioned the same result as me with only getting 12v with the engine running... but i could have swore i have tested this in the past and have gotten +12v with the key on.

FWIW im tracing down a low idle, lean tip-in and "staying" rich condition.

Most of the time when pressing the accelerator i will go lean for a second or two and then go back to stoich. Sometimes when i let off the gas, the engine will go rich and stay there until i press the accelerator again. Weirdness
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  #64  
Old March 18th, 2012, 11:34
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Re: Testing Jeep O2, Oxygen sensors

My 89 and 87 are hot with engine off, in the ignition switch run mode. I guess the 90 ECU could be smart enough to only power once the engine is running, but I don't know if it is different. Sounds like something is not right.

Mine are very slow to recover to stoich on decel, like 10-15 seconds, but fast recover on acceleration, about 2 seconds.

Not sure where your test points are, but I would check the grounds, ALL of them!!! Wiggle tests, the works.
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  #65  
Old March 19th, 2012, 23:42
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Re: Testing Jeep O2, Oxygen sensors

Ive confirmed that its by design on the 90 MY to only energize the 02 heater element for 5 seconds after turning the key on. Its tied into the starter relay which also supplies +12v through the Fuel Pump Ballast Resistor.
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  #66  
Old March 20th, 2012, 07:19
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Re: Testing Jeep O2, Oxygen sensors

Interesting, so I wonder happens if one puts a 90 ECU on and older Renix rig. Since it is just a pre start difference, I guess it does matter. IIRC we tested an HO rig one day with out the motor on and got the 12 V, but I am not 100% positive. I guess the lesson, check it with the engine running, if there is any doubt.
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  #67  
Old April 9th, 2012, 09:30
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Re: Testing Jeep O2, Oxygen sensors

http://www.naxja.org/forum/showthrea...=947676&page=2

I can confirm that a 90 remix does not energize the relay until the engine is running... To be specific it is energized in the same way as the fuel pump... Power gets shut off to it if the ignition is left on without the engine running after a few seconds. You can hear the relay click off. Test voltage with engine running and o2 sensor plugged in if you want to avoid the saga I had with a faulty relay.

I have a new interesting issue. My 90 is again running a little smelly at idle. The o2 sensor test shows a swing only a volt or 2 from 2.46 at idle so it is like the ecu thinks it is running at 2000 rpm. This is a new old engine from the last saga. The old engine had a ton of blow by... Moved the manifolds and sensors over to the new block. First step is. To swap out the sooty egr valve. More to come
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  #68  
Old April 15th, 2012, 19:02
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Re: Testing Jeep O2, Oxygen sensors RENIX Manual is right

It has been mentioned in other threads that the RENIX version how o2 content is measured is a little different than you would expect. It is pretty confusing and totally counter-intuitive.

From the RENIX manual

"When the oxygen content is low, (rich mixture), the voltage signal will be less than 2.5 volts. A lean mixture (high oxygen content) the voltage is signal is above 2.5 volts."

So
1 volt = rich
5 volts = lean
2.5 just right....

(more o2= lean mixture = lower resistance = higher voltage ???)

From wikipedia which quotes other references so it must be true.

"So, for fuel-rich exhaust (lower oxygen concentration) the resistance is low, and for fuel-lean exhaust (higher oxygen concentration) the resistance is high."

(more o2= lean mixture = higher resistance = lower voltage )


Another reference

http://www.hybridconversions.com/v/v...0explained.pdf

As titania is an N-type semiconductor with a structure TiO2-x, the x defects in the crystal lattice conduct the charge. So, for fuel-rich exhaust the resistance is low, and for fuel-lean exhaust the resistance is high.
(more o2= lean mixture = more resistance = lower voltage) same language that wikipedia uses)

(more o2= lean mixture = higher resistance = lower voltage )

Anyway I spent some time on this today and I think I can confirm that the RENIX ECU will see high voltage as rich and low as lean. I had a bad fuel pressure regulator and it caused the o2 sensor to read less than 1 volt consistently at idle. This drove me crazy and I am hoping this research helps others that are struggling with the same troubleshooting dilemma. If you have a RENIX sensor that consistently reads less than 1 v after warmup something is causing it to run rich and it is likely to be the fuel pressure regulator. It means the o2 sensor is functioning properly.

Think that this is confusing because you have multiple reverse logic things happening.

Higher resistance = lower voltage higher o2= less resistance = higher voltage... arghh!!!


So I smelled a rat and decided to read the bloody patent. Which I have linked to and list the relevant excerpt below. It would appear that Titania sensor's resistance actually decreases with the amount of o2 in the stream. It is an inverse relationship....

(more o2= lean mixture = lower resistance = higher voltage )

I am going to challenge Wikipedia on this unless anyone sees what I am sure I am missing.


http://www.google.com/patents?id=pFI...1792 &f=false





Done.
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  #69  
Old April 17th, 2012, 22:02
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Re: Testing Jeep O2, Oxygen sensors

Read it again, the patent says that Wiki is right and the FSM is wrong (if in fact the FSM is reversed?).

One thing you missed, to add to the confusion, is that if the engine is running rich due to a leaking fuel injector (say on one cylinder) or FPR, the ECU may be fighting the leak by trying to run the rest of the engine lean, and if there is an exhaust manifold leak near the O2 sensor, all bets are off as to what the O2 sensor reading really means!!!

I am pretty sure (IIRC) that a high voltage O2 sensor reading on renix, is a rich, excess fuel reading. I will try and dig up my old notes later when I get time, but reread the bottom text of your patent post, it says high voltage is rich, excess fuel.
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  #70  
Old April 17th, 2012, 23:32
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Re: Testing Jeep O2, Oxygen sensors

Yeah I am totally confused but after sleeping on it I am thinking you are maybe right. The first part of the excerpt does say low resistance when 02 low which would mean higher voltage. Why the Jeep would smell rich and the 02 would indicate lean is bugging me. I can get it to go into closed loop IF I get it hot. Otherwise it will run .25 volts... I like the leaky injector idea. More to come.
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  #71  
Old April 18th, 2012, 07:23
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Re: Testing Jeep O2, Oxygen sensors

Have you checked both O2 sensor grounds for less than 1 ohm, power off.

Have you checked for the 12-14 volts to the heater in the O2 sensor????
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  #72  
Old April 19th, 2012, 00:02
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Re: Testing Jeep O2, Oxygen sensors

So I hate to admit this. When I pulled the fuel rail to test the injectors I noticed a vacuum leak on the manifold the size of Texas. Fixed it and I am back to closed loop. Silly me.
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  #73  
Old April 19th, 2012, 06:59
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Re: Testing Jeep O2, Oxygen sensors

What was leaking? Glad you fixed it.
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  #74  
Old April 19th, 2012, 09:13
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Re: Testing Jeep O2, Oxygen sensors

The hose from the orifice qnext to the IAT sensor was hiding behind the exhaust manifold I saw it as soon as I started removing parts. Engine idle was compensating perfectly.
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  #75  
Old June 10th, 2012, 12:19
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Re: Testing Jeep O2, Oxygen sensors RENIX Manual is right

Update on this:

I was wrong:

Renix O2 sensor Voltage below 2.5 V IS RICH, above 2.5 V IS LEAN.

The Renix MPFI FSM is right. The problem is the language used, and the fact that there are two resistors in the circuit, and they use language like "the Voltage Drop increases", where using the word drop with increases on page 42 of the FSM in Fig 21 makes it very confusing, easy to miss read as Voltage increases, when it means the opposite, then they swap resistors in mid speech as well (one resistor plays off the other), LOL!

No wonder we keep getting confused as to who is on first and what is on second, LOL.

Also keep in mind that if the ECU thinks it sees a high voltage and the O2 sensor voltage is actually low, the ECU will react to further lower the low voltage, as it is not seeing the true sensor data (which will confuse most people trying to diagnose the problem)! This can be caused by wiring issues, open or shorted wires....



Quote:
Originally Posted by nickguy View Post
It has been mentioned in other threads that the RENIX version how o2 content is measured is a little different than you would expect. It is pretty confusing and totally counter-intuitive.

From the RENIX manual

"When the oxygen content is low, (rich mixture), the voltage signal will be less than 2.5 volts. A lean mixture (high oxygen content) the voltage is signal is above 2.5 volts."

So
1 volt = rich
5 volts = lean
2.5 just right....

(more o2= lean mixture = lower resistance = higher voltage ???)

From wikipedia which quotes other references so it must be true.

"So, for fuel-rich exhaust (lower oxygen concentration) the resistance is low, and for fuel-lean exhaust (higher oxygen concentration) the resistance is high."

(more o2= lean mixture = higher resistance = lower voltage )


Another reference

http://www.hybridconversions.com/v/v...0explained.pdf

As titania is an N-type semiconductor with a structure TiO2-x, the x defects in the crystal lattice conduct the charge. So, for fuel-rich exhaust the resistance is low, and for fuel-lean exhaust the resistance is high.
(more o2= lean mixture = more resistance = lower voltage) same language that wikipedia uses)

(more o2= lean mixture = higher resistance = lower voltage )

Anyway I spent some time on this today and I think I can confirm that the RENIX ECU will see high voltage as rich and low as lean. I had a bad fuel pressure regulator and it caused the o2 sensor to read less than 1 volt consistently at idle. This drove me crazy and I am hoping this research helps others that are struggling with the same troubleshooting dilemma. If you have a RENIX sensor that consistently reads less than 1 v after warmup something is causing it to run rich and it is likely to be the fuel pressure regulator. It means the o2 sensor is functioning properly.

Think that this is confusing because you have multiple reverse logic things happening.

Higher resistance = lower voltage higher o2= less resistance = higher voltage... arghh!!!


So I smelled a rat and decided to read the bloody patent. Which I have linked to and list the relevant excerpt below. It would appear that Titania sensor's resistance actually decreases with the amount of o2 in the stream. It is an inverse relationship....

(more o2= lean mixture = lower resistance = higher voltage )

I am going to challenge Wikipedia on this unless anyone sees what I am sure I am missing.


http://www.google.com/patents?id=pFI...1792 &f=false





Done.
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