Heater circuit

Codes pulled

 

The o2 sensors seem to have proper ohms at 3.6 but I never got much voltage of the feed connects hints the code I guess. What wld stop the heater circuit from getting proper voltage

 

In the 2005 FSM it seems the 12V supply to all of those is individually supplied by the PCM. But, this doesn't match the text in the fuel section which describes the 12V supply being fed by the O2 heater relay in the Power Distribution Center (PDC) under the hood. Have a look at the inside of the lid of your PDC. If there is an O2 sensor relay swap it with one of the others if there is one the same in there and look for a blown fuse too. If you have a blown fuse there may be some wiring that has got chafed or burnt and shorted to ground.

If the is no O2 relay have a look at the ground connector on the block near the oil filter. All of the O2 sensor heaters ground there.

 

No relay or fuse as far as I can tell labeled that way . Ground on block seems tight . Thank you for ur help by the way . My dang tags r expired and this problem is killing me lol

 

No relay or fuse as far as I can tell labeled that way . Ground on block seems tight..

Fuse #16 is for your O2's. Its in the PDC under your hood. Relay #34 is in the PDC also and is also for your O2's. Now take johnny's advice and report back.

 

Just had a thought. Found this thread that might be related to your problem...

http://www.jeepforum.com/forum/f9/02-sensors-wont-ready-codes-after-replacing-02s-read-try-1447579/

 

Thank u again . Maybe I need this rewire since I've yet to find anything else . Sadly I don't know much about jeeps or automobiles in general so I cld definetly b missing something . With the expensive unknown like cats , o2 sensors etc I'm worried about taking it to a shop . Only to have them changing parts to hunt it down .

 

I know what the text says in the fuel section of the '05 FSM but the diagram in the wiring section 8W-30 is correct on my (CA) '05. No O2 relay & fuse 16 bay is empty. I think that changed between '04 & '05. I'm pretty sure there are 4 power wires from the PCM that power the heaters but there is a common ground. While it is possible that all have low voltage from the source inside the PCM it seems also possible & more probable that there is high resistance to ground which for all 4 to be affected would have to be at the common grounding point. You can test for 12v to each sensor after unplugging each connector. Then check continuity to ground.

If the sensors were not readying you would get the flashing CEL as described in the link within the link given above & that would be giving a different set of codes, I think.

 

The ground circuit shld just have continuity opened or closed ?and not a resistance right ?

 

With them unplugged the ground wires (black/light green & black/light blue, 2 each) should have no resistance to ground. If they do have resistance & it is the same (more or less) that would indicate the resistance is at the point where they are all grounded together (noted above). I would think that would be the case since they are all apparently throwing the code indicating the same problem for all. Possibly a bad crimp if the 4 are crimped into one terminal.

If they all happen to have low voltage & more or less equal at the power wire that would indicate a PCM problem since each comes from the PCM & probably one single source within the PCM.

 

With them unplugged the ground wires (black/light green & black/light blue, 2 each) should have no resistance to ground. If they do have resistance & it is the same (more or less) that would indicate the resistance is at the point where they are all grounded together (noted above). I would think that would be the case since they are all apparently throwing the code indicating the same problem for all. Possibly a bad crimp if the 4 are crimped into one terminal.

If they all happen to have low voltage & more or less equal at the power wire that would indicate a PCM problem since each comes from the PCM & probably one single source within the PCM.

That mod is for readiness but certainly can't hurt trying. I have seen that TSB but it is not clear to me how it actually causes them to ready any sooner.

I assume you should be getting 12v at the power wire for the heaters. In earlier yrs they used a relay/fuse & it was obvious that they were getting 12v to them. But in these later yr systems the "magic" happens in the PCM so don't know for sure.

Be sure you have the heater wire not the sensor wire(s). Sensors 1/1 & 2/1 are brown/light green (1/1) & brown/violet (2/1), pin 1 in those connectors. Sensors 1/2 & 2/2 are brown/white (1/2) & brown/grey (2/2), & pin 4 in those connectors.

Johnny getting ready to try tsb mod. I hope it works . I'll post results tonight I hope it is instant I hate to wait on resets

Checking both 12v & ground requires one probe connected to the battery (-) post or any GOOD ground. It is best to go to the battery though. For ground you use the continuity or ohms scale. 0 ohms = continuity & probe the ground terminal in the harness connector. Then for the voltage switch the meter to something like 20vdc & probe the power wire in the connector & read the meter voltage.

Finding the correct wire for each sensor is necessary & they have different colors so be sure you get them right. The upstream sensors (above the cats) are 1/1 front pipe & 2/1 back pipe. Then the downstream are 1/2 front & 2/2 back. Colors are noted above.

 

2 to 4 volts only to each of the feed connectors for unplugged o2 sensors . Is it suppose to b 12v? And if so does that mean the pcm must b replaced . Also do that tsb wiring reroute change any of this ?

 

Just had a thought. Found this thread that might be related to your problem... http://www.jeepforum.com/forum/f9/02-sensors-wont-ready-codes-after-replacing-02s-read-try-1447579/

Johnny getting ready to try tsb mod. I hope it works . I'll post results tonight I hope it is instant I hate to wait on resets

 

That mod is for readiness but certainly can't hurt trying. I have seen that TSB but it is not clear to me how it actually causes them to ready any sooner.

I assume you should be getting 12v at the power wire for the heaters. In earlier yrs they used a relay/fuse & it was obvious that they were getting 12v to them. But in these later yr systems the "magic" happens in the PCM so don't know for sure.

Be sure you have the heater wire not the sensor wire(s). Sensors 1/1 & 2/1 are brown/light green (1/1) & brown/violet (2/1), pin 1 in those connectors. Sensors 1/2 & 2/2 are brown/white (1/2) & brown/grey (2/2), & pin 4 in those connectors.

 

Well I completed the mod and the check engine light came back on after a drive since battery was disconnected . I haven't read the codes or checked for voltage since the mod but it's not looking good. My codes were never for readiness that I cld tell but for low voltage and relay circuit low . Idid however have the check engine light blink after a few seconds and the go solid (with engine not cranked) just noticed today. Cld have always been . I've exhausted my options and will try a local shop and post the results thanks to everyone

 

That mod is for readiness but certainly can't hurt trying. I have seen that TSB but it is not clear to me how it actually causes them to ready any sooner. I assume you should be getting 12v at the power wire for the heaters. In earlier yrs they used a relay/fuse & it was obvious that they were getting 12v to them. But in these later yr systems the "magic" happens in the PCM so don't know for sure. Be sure you have the heater wire not the sensor wire(s). Sensors 1/1 & 2/1 are brown/light green (1/1) & brown/violet (2/1), pin 1 in those connectors. Sensors 1/2 & 2/2 are brown/white (1/2) & brown/grey (2/2), & pin 4 in those connectors.

Above mentions the color of the sensor wires correct at the connectors ? I've checked them all but to be clear the heater circuit wires are both the same color(white) to each sensor. The heater
circuit is where I want to check for12v

 

I'm using the colors from the wiring diagrams in my '05 FSM. That should be the colors to the connectors not the wires for the sensor pigtails. It may be the white wire & I'm guessing it would be the same on all 4 sensors, but not positive. As noted earlier, you need to unplug the sensors & check for 12v (again assuming it should be 12v as the earlier ones were) with the key on & continuity to ground from the harness side connectors.

The other 2 wires for each sensor are for the sensor signal & return, not affected by the codes you are getting.

 

I had the same codes, did the TSB but it didnt fix it. The dealer diagnosed it as a bad PCM so I swapped in a new/refurb one and it fixed it.

 

I disconnect connector ,one side goes to the sensor and has 4 female ports and the connector attached to the harness has male pins and there are 4 of them. Two for sensor and two for heater . . Check one male pin for 12v and check one for continuity ? When checking continuity on a line like this do I put one of the multi meters probes on the pin and the other probe on the battery negative to see that it is continuous or what?

 

Something I forgot to mention was I've been having the death wobble bad sometimes and more than a few times the battery cables had loosened enough that next time I got in jeep to start it wldnt and I wold have to tighten cables to restart. Think that cld have damaged my Pcm or something else causing this problem. I did probe the two pins for heater circuit on b1-s-1 and b2-s2 and got less than one volt with my probes on both heater pins . Since I was able to read a volt using the neutral pin does that mean that neutral is a good wire .?

 

Only if the "neutral" pin has a GOOD ground. If there is excessive resistance in that (ground) wire it will affect the voltage reading. As noted earlier, a bad (high resistance) ground could be the problem causing the codes so first you need to check the ground wire(s). I also emphasized that the meter had to be probed to a GOOD ground like the battery post for this reason.


Lose cables should not hurt the PCM but anything is possible.


I am not understanding the "b1-s-1 and b2-s2" so hope you are finding the correct pins for heater power.

 

I am not understanding the "b1-s-1 and b2-s2" so hope you are finding the correct pins for heater power.

I think he means bank 1-sensor 1, etc...

 

ok so I'm trying here... hopefully y'all can re into my stupidity. i was having trouble understanding the wiring as it seems mine was different or something I'm retarded basically. so i took numbers from every pin on harness side of 02 connector.

bank1/sensor 1
brown/w lightgreen .798 v and 0 ohm
blk/ w light green 1.7 v and 16.7 ohm (only one to beep on contiunity)
blue /w light blue 4.17 v and 11.9 ohm
brown /w blueish green ? 2.4 v and 11.4 ohm
bank2 sensor1
blk / w green 1.7 v and 16.2 ohms ( only one to beep on continuity)
brown w/ violet .958 v and 32 ohm
blue w/ light green 4.25 v and 11.9 ohm
br w/ green 2.4 v and 11.9 ohm
bank1 sensor 2
blk w/ blue 1.7 v and 11.7 ohm (only to be on continuity)
brown w/ white .96 v and 31 ohms
blue w/ light green 4.1 v and 10.7 ohms
blue wire 2.4 v and 13 ohm
bank 2 sensor 2
brown wire 4.2 v and 10.95 ohm
br w/ white 1.6 v and 0 ohm
blk w/ blue 3v and 29 ohm (only to beep on continuity)

a lot i know but seemed again like i clint see colors right or mines different idk. but maybe it'll make sense to y'all .
blue wire 2.4 v and 11.7 ohm

 

ok so I'm trying here... hopefully y'all can re into my stupidity. i was having trouble understanding the wiring as it seems mine was different or something I'm retarded basically. so i took numbers from every pin on harness side of 02 connector.

bank1/sensor 1

brown/w lightgreen .798 v and 0 ohm ............................................... heater control should be 12V
blk/ w light green 1.7 v and 16.7 ohm (only one to beep on contiunity)... (brown?/light green) heater ground, 0 ohms.
blue /w light blue 4.17 v and 11.9 ohm............................................... sensor signal
brown /w blueish green ? 2.4 v and 11.4 ohm ..................................... upstream sensor return

bank2 sensor1

blk / w green 1.7 v and 16.2 ohms ( only one to beep on continuity)...... heater ground, 0 ohms.
brown w/ violet .958 v and 32 ohm ................................................. heater control 12V
blue w/ light green 4.25 v and 11.9 ohm ........................................... sensor signal
br w/ green 2.4 v and 11.9 ohm ...................................................... sensor return

bank1 sensor 2

blk w/ blue 1.7 v and 11.7 ohm (only to be on continuity)...... heater ground, 0 ohms
brown w/ white .96 v and 31 ohms .................................... heater control 12V
blue w/ light green 4.1 v and 10.7 ohms ............................. (dark blue/yellow?) sensor signal
blue wire 2.4 v and 13 ohm .............................................. (dark blue/dark green) sensor return

bank 2 sensor 2

brown wire 4.2 v and 10.95 ohm .................................. sensor signal
br w/ white 1.6 v and 0 ohm ....................................... (brown/grey?) heater control 12V
blk w/ blue 3v and 29 ohm (only to beep on continuity).... heater ground 0 ohms
blue wire 2.4 v and 11.7 ohm ...................................... sensor return wire.

a lot i know but seemed again like i can't see colors right or mines different idk. but maybe it'll make sense to y'all .

Colours can fade and change hue over the years so where I think you are seeing them wrong I've added what I think the wires should be.
The wires you need to be concentrating on are the heater control and ground wires. You can ignore the sensor signal and return wires as they are unrelated to the issue at hand.

I'm not sure when the heater control wires will have 12V on them since they are controlled by the PCM and won't be on all the time. I'd expect them to initially come on in a similar way to the ASD relay so on for the first two seconds and during engine cranking. After that I presume they can be switched on and off as the PCM sees fit. I'd get someone to cycle the ignition on and off while looking for 12V on those wires.

Since you said the heaters ohm out at 3.6 ohms and your ground resistances are higher than this the ground connection could well be your problem, as the resistance on those wires will massively reduce power to the heaters making them ineffective. If you've not done it already, remove the ground wires from the engine block and clean them all up, then refasten them securely. Once done recheck the resistance of the ground wires.

 

Ok I will disconnect and clean as I have only just snugged up the bolt to make sure it wasn't loose (the ground on the block) .
I spoke with another gentleman and he said best way to test the ground was with jumpers and a test light . if light is dim or doesn't light ground issue if it does light then a sensor , heater driver circuit (which idk what that is ) or pcm is issue .

 

Ended up at an auto shop on this problem . They said all o2 sensors check out but when they pinned pcm it proved rob the issues.they want 1050$ to install new included parts and labor .if I bought my own wld y'all rec me installing it ? Or does it have to b programmed ?

 

Just picked loucile.the check engine light is off and I am the proud new owner of a pcm . Mechanic said the system had not yet readied itself and wld need more of a drive cycle . So I guess till not 100%sureyet I'm fixed . I'll post again iterate all good.