8Mud
NAXJA Forum User
- Location
- Central Germany
Don't confuse normally open and normally closed with normally energized and normally de-energized.
-
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Testing Jeep O2, Oxygen sensors
- Thread starter Ecomike
- Start date
Its the same thing. Unless you can explain the difference.
- Location
- MilkyWay Galaxy
Indeed it does, on Renix, it delays the power off time after turning the ignition switch off such that the ECU has extra time to reset the IAC for a restart air flow rate of IAC (versus a hot idle air flow rate), as I recall.
- Location
- MilkyWay Galaxy
In the ignition off position, it would be normal to design it as a NO relay, powered to close with the engine running, once it started, but when you task broke AMC folks, and Bendix engineers and those French boys to design a whole new critter called Renix, who knows what they did. :laugh3:
To me a normally closed relay would mean power is going to the heater in the O2 sensor 24/7, which it is not. That would kill the battery. I assumed that is how it was wired, as I had never heard any different......
As 8MUD posted:
"Don't confuse normally open and normally closed with normally energized and normally de-energized. "
and you asked, .......
Well, 8MUD is right, They are not the same.
NC is a mechanical position of the relay as a loose part not connected to anything. In this case, from what Nick posted on Facebook, the O2 sensor heater power relay is according to him:
NC normally closed as a relay by itself, but there is no power to the output side of the relay until the ignition switch is in the run position and thus powering the start(?)/run(?) relay
(little old style rectangular relay very close to the battery) with a hoard of wires with fusesable link wires on it
That then sends 12-14 volts to the O2 sensor heater relay output side of the relay. That is why the NC (I was wrong) relay does not drain the battery...
It seems the relay is only there, according to Nick, to cut power (via an ECU command of power to the relay coil to make it Open???) to the heater in the O2 sensor at WOT????
I trust he knows what he is talking about, as that is too convoluted to make it up, LOLOL. :laugh3:
I know one thing for sure, even I can not make this shit up LOLOL.
I never in a million years would have considered it possible they would have done something like that.
No wonder Renix seems so goofy at times to most folks.
So power must get from the Relay at the battery,
though a fuse link wire,
to the O2 sensor Heater relay
then to the O2 sensor.
And the Ignition switch powers the main relay at the battery.
Then the O2 sensor heater has power,
unless the ECU powers the Heater relay to open and only that should happen at WOT according to Nick.
8MUD, check out the 1000 + Renix jeep owner folks group on Facebook. Lots of young-uns there daily looking for help and advise from us oldtimers, and Nick is there too, the guy that created the Renix scanners (over 200+ built and sold IIRC?) and hacked the Renix code.
This will explain it all. A good education for all who question relay operation.
https://www.12voltplanet.co.uk/relay-guide.html
So then it sounds that it's possible then that it is either the starter relay or a fusable link that is causing my battery to drain with Key off.
Thanks EcoMike for that insight.
- Location
- MilkyWay Galaxy
I thought one of the four relays had a different part number and had a fifth pin? I think my Wagoneer does, but I could be wrong. I have never had to replace on in 15 years on 5 Renix rigs yet, so I am not sure.
- Location
- MilkyWay Galaxy
I was already wondering that about two I have had off and on problems with unexplained drained batteries that most blame on interior lights and door switches.
It would have to be a sticking starter relay by the battery. The fuse link would not, could not cause it, and I smoked mine once with a short in the O2 sensor harness cable that smoked a neighborhood once :shiver: with out the fuse link dying.
It would have to be a sticking starter relay by the battery. The fuse link would not, could not cause it, and I smoked mine once with a short in the O2 sensor harness cable that smoked a neighborhood once :shiver: with out the fuse link dying.
8Mud
NAXJA Forum User
- Location
- Central Germany
The significant drains I've had are the glove box, the light never went out. The second was a bundle of wires running under the drivers side carpet, the splices crossed other splices and the whole wad was green corroded and passing current to ground and/or each other. Water and mud had leaked inside my starter relay and turned to mud soup, which also caused a sizable short to ground or cross leak. I once put a mounting screw for the drivers side bottom sill through a harness. Renix connectors are prone to corrosion, and oxides conduct somewhat, especially the under hood connectors.
I did a search on how to tell if a fuse link goes bad and it is fairly obvious because the wire on either end of the rubber piece gets ugly.
So mine are still good. Hopefully it is the starter relay as the cause of my o2 heater wire being hot constantly.
For sure. My starter relay connectors were terrible and the relay holder connectors are as bad. I imagine that northern climates would even be worse.
NickInTimeFilms
NAXJA Forum User
- Location
- NJ
I'm playing catch up, and I think through all the links you've got the relays down but just incase, let's run from the top:
Correct, NO and NC Relays are available. If you look at the diagrams provided in that data sheet, you will see that NO is a 4 pin relay. NC is a 5 pin relay. Both relays have the same pin numbers wired the same way. The NO is missing pin 87a, (The NC pin.)
Relay Basics:
The standard bosch cube relay is very commonly used in the automotive world and is used all over the Renix system.
It comes in a 4pin and 5pin version, as well as different amp ratings, but all the pins are wired the same.
The Low Power side is a coil that will open and close the High Power contacts.
Pin 86 of the coil is the Positive Side.
Pin 85 of the coil is the Negative Side.
Run 12v through the coil to turn it on, disconnect from 12v to turn off.
The High Power side is what actually takes the load power for the system in question, and sends it where it needs to go.
Pin 30 of the Contacts is the Positive Input to supply the Load power. (12V IN)
Pin 87 of the Contacts is the Normally Open (Normally OFF) contact connected to the load. (12V OUT when ON.) This will get load power when the Coil is ON and works how you would expect.
Pin 87a of the Contacts is the opposite of 87. It is the Normally Closed (Normally ON) contact connected to the load. (12V OUT when OFF.) This will get load power when the Coil is OFF, and turn off when the coil is on; opposite of a normal switch.
With all that in mind, you can understand how any 4 or 5 pin relay works.
Coil ON = 12v from 30 to 87.
Coil OFF = 12v from 30 to 87a.
Now then, back to the issue.
Have you absolutely confirmed that the o2 relay is the source of your battery drain?
If you unplug the o2 sensor, do you still have a battery drain issue?
Post #171 goes over the wiring, sourced directly from the 1990 Factory Service Manual.
The o2 relay gets its 12v input power (PIN 30) from the fuel pump relay output (PIN 87.) So the fuel pump relay turns on and sends power to the o2 sensor.
This is an odd chain of command since usually PIN 30 is a steady power source such as 12v hot or 12v ignition, but instead the Input power is getting turned on and off by something else for the o2 to work.
This is part of the reason why 87a NC is used to feed the o2. The o2 is actually turned on and off mainly by the fuel pump relay. The o2 Relay is only used so that the ECU can then turn it off later if it deems necessary.
Page 604 (8W-181, MJ-XJ 20) shows the wiring diagram in question here.
I hope that clears this marvelous Renix design up just a bit. Please do some basic elimination testing so we can see if removing the o2 or o2 relay changes the issue, or if we should look elsewhere.
Correct, NO and NC Relays are available. If you look at the diagrams provided in that data sheet, you will see that NO is a 4 pin relay. NC is a 5 pin relay. Both relays have the same pin numbers wired the same way. The NO is missing pin 87a, (The NC pin.)
Relay Basics:
The standard bosch cube relay is very commonly used in the automotive world and is used all over the Renix system.
It comes in a 4pin and 5pin version, as well as different amp ratings, but all the pins are wired the same.
The Low Power side is a coil that will open and close the High Power contacts.
Pin 86 of the coil is the Positive Side.
Pin 85 of the coil is the Negative Side.
Run 12v through the coil to turn it on, disconnect from 12v to turn off.
The High Power side is what actually takes the load power for the system in question, and sends it where it needs to go.
Pin 30 of the Contacts is the Positive Input to supply the Load power. (12V IN)
Pin 87 of the Contacts is the Normally Open (Normally OFF) contact connected to the load. (12V OUT when ON.) This will get load power when the Coil is ON and works how you would expect.
Pin 87a of the Contacts is the opposite of 87. It is the Normally Closed (Normally ON) contact connected to the load. (12V OUT when OFF.) This will get load power when the Coil is OFF, and turn off when the coil is on; opposite of a normal switch.
With all that in mind, you can understand how any 4 or 5 pin relay works.
Coil ON = 12v from 30 to 87.
Coil OFF = 12v from 30 to 87a.
Now then, back to the issue.
Have you absolutely confirmed that the o2 relay is the source of your battery drain?
If you unplug the o2 sensor, do you still have a battery drain issue?
Post #171 goes over the wiring, sourced directly from the 1990 Factory Service Manual.
The o2 relay gets its 12v input power (PIN 30) from the fuel pump relay output (PIN 87.) So the fuel pump relay turns on and sends power to the o2 sensor.
This is an odd chain of command since usually PIN 30 is a steady power source such as 12v hot or 12v ignition, but instead the Input power is getting turned on and off by something else for the o2 to work.
This is part of the reason why 87a NC is used to feed the o2. The o2 is actually turned on and off mainly by the fuel pump relay. The o2 Relay is only used so that the ECU can then turn it off later if it deems necessary.
Page 604 (8W-181, MJ-XJ 20) shows the wiring diagram in question here.
I hope that clears this marvelous Renix design up just a bit. Please do some basic elimination testing so we can see if removing the o2 or o2 relay changes the issue, or if we should look elsewhere.
- Location
- MilkyWay Galaxy
Impressive, most Impressive post. No wonder you were able to hack Renix LOL.:laugh3:
This whole thing has got my head aching. There has been a couple work arounds by one of the previous owners that I have not mentioned.
One is a jumper wire that goes between the o2 relay and the fuel pump relay. It's there to get the fuel pump to run off of the o2 relay.
The other is two wires were cross connected on the AC relay. Why??? Don't know but the ac works.
The engine had been running fine ever since I got it, three years or so. That is until recently it started stalling at stop lights.
I did find a burned wire on the ignition switch just recently and replaced the switch. The switch had been catching when turning the key to the off position, been like that ever since I got the jeep. Don't know if the catching finally caught up with me and recently burned the wire or if it had been like that ever since. It looked bad but the wire and connector were intact.
Anyway I started a thread on the whole GIANT mystery at the Cherokee Forum a few weeks ago. A huge shout out for 'Dave51' who has been so kind as to follow it and trying his hardest to figure it out. I guess he like puzzles. Hats off to him for sticking with it for so long. If it had not been for him I would have given up a week ago.
If you are interested and like a big mystery you can check it out at the following link and get all the details. There was so much discussed that it would be a huge undertaking to try and summarize it all here.
It begins with me blaming aftermarket o2 sensors for my battery drain along with a couple short videos of the engine running connected to a mt2500.
And then I made a big discovery as to the source of the real cause of the battery drain. At least the discovery cleared the o2 sensors for being at fault.
https://www.cherokeeforum.com/f2/o2-sensor-issues-251391/
There is a jumper wire sharing pin 85 on the fuel pump relay and pin 85 on the o2 relay.
Here is what I get for o2 power wire with jumper wire in and out, fuel pump relay in and out and the o2 relay in and out.
O2 and FP relay in with jumper wire out got power with key on.
O2 and FP relay out with jump wire in got no power with key on or off.
O2 relay out with jump wire in got no power with key on or off.
O2 relay out and jumper wire out got no power with key on or off.
FP relay out and jump wire out got power with key on.
FP relay out with jumper wire in got no power with key on.
My question to you Nick is with the jumper wire in place the jeep runs fine except the o2 gets power all the time and burns out the o2.
Will this prevent a wideband o2 from working correctly being that the wideband only uses the 5v reference wire and the hot wire is eliminated?
Here is what I get for o2 power wire with jumper wire in and out, fuel pump relay in and out and the o2 relay in and out.
O2 and FP relay in with jumper wire out got power with key on.
O2 and FP relay out with jump wire in got no power with key on or off.
O2 relay out with jump wire in got no power with key on or off.
O2 relay out and jumper wire out got no power with key on or off.
FP relay out and jump wire out got power with key on.
FP relay out with jumper wire in got no power with key on.
My question to you Nick is with the jumper wire in place the jeep runs fine except the o2 gets power all the time and burns out the o2.
Will this prevent a wideband o2 from working correctly being that the wideband only uses the 5v reference wire and the hot wire is eliminated?
NickInTimeFilms
NAXJA Forum User
- Location
- NJ
Hmm, custom wiring headaches makes this even more fun, oh boy.
So from the diagram, it looks like 85 for both o2 and fuel pump go to the same place anyway. They should both be yellow wires that get power with ignition on. Both 86 terminals are grounded by the ECU on separate pins to complete the circuit.
I tried to make a truth table, but came up inconclusive. I'm assuming that we will get power when the o2 relay is in, other inputs don't matter.
O2 FP JP KF KO
1 1 x ? 1
x x 1 x x
x ? 1 x x
x ? x x x
? x x ? 1
? x 1 ? x
I would check pin 30 on the o2 relay next to see what's going on. Does it have power all the time, power with key on, or only power when engine running? It should only have power with KOEO.
As for a wideband setup, it would work regardless of the current system since it's all separate. It is activated with the included gauge driver or other included device, and the only working part of the factory system needed is the 5v ref line for signal in. Technically since the REM makes its own voltage with don't even need the 5v ref, just that the ECU is reading a voltage change on the line.
Pin 30 on O2 relay gets power key on, key off as well as with the negative battery terminal disconnected. This is with or without the jumper wire between o2 relay pin #85 and fuel pump relay pin #85. Only way fuel pump runs is with that jumper wire installed.
The A/C clutch relay wire (orange/black), that goes to pin #86 is crossed with (Light green), wire that goes to pin #87.
Note: Have not reconnected the Or/Bl to Or/Bl and Gr to Gr wires as not sure what will happen. (See Dave51 Theory below).
Did A/C relay holder voltage test on the Or/Bl pin #86 and Lt Gr wire pin #87
Key Off Negative battery terminal off 12v
Key on Negative battery terminal off 12v
Key on Negative battery terminal on .01v
Interesting to note: Tested several times, sometimes the voltage test would begin at 10.7v + or - and slowing increase to 12v plus volts.
=============================================================================
Dave51 over at Cherokee forum had a theory on the A/C (Or/Bl wire pin 86) and (Gr wires pin 87) being switched.
Normally the fuel pump relay provides B+ power to the clutch relay switch. When AC switch is turned on ECU completes that circuit, engages the clutch relay, and as long as the low pressure switch is engaged the AC control switch runs the AC.
With the wire switch, the AC clutch will receive power directly from the fuel pump relay, but the AC clutch relay switch is controlled by the AC control switch, which now controls both the AC Clutch and the AC. Since both of those circuits are 12V it doesn't make any difference.
As to why the change, got me. Perhaps after the fuel pump relay problem (and there still is a fuel pump relay problem) the AC didn't work (because Orange/Black was dead). The PO changed Lt. Gr. and Orange/Bl in an attempt to energize AC Clutch Relay, but of course it wouldn't work. Then the jumper idea came up and now the AC works so he just left it.
NickInTimeFilms
NAXJA Forum User
- Location
- NJ
Ding ding, we have a weiner. So it looks like the o2 heater input was swapped to a 12v hot source at some point which is causing your battery drain.
At the very least, I would switch o2 heater pin 30 to an ignition source so it only works with key on, but ideally it should be run to pin 87 of the fuel pump relay so it's only on when the engine is running.
This should help your battery drain issue just a bit depending on how much else was changed. :roll:
That was funny Nick... "Ding ding, we have a weiner"
In order to run pin 30 of the o2 relay to pin 87 of the fuel pump relay is it a simple matter of disconnect the o2 pin 30 wire and reattaching it to the FP pin 87?
I don't imagine it would be wise to run a jumper as it will only create the same issue or make it worse.
And if that is correct and I did that, would the ECU be able to cut power to the heater when it's not needed?
Also would that mess with fuel trims?
