P0125 error code - help!

[Olaf]

Beware of sheathing on the blue wire, kept from contact with inner wire at connection. No more CEL, mileage around 12 city 13.5 highway. Hear about guys with better mileage, must not have AT's.

'97lx, 290,000 arb, mate blk, emu lift, engine rebuilt, etc...

 

[lndcruz]

So am I understanding correctly that your issue was a rear o2 sensor wiring issue? I have been having the same issue after replacement of most of the same parts.

 

[NavyDiver82]

So am I understanding correctly that your issue was a rear o2 sensor wiring issue? I have been having the same issue after replacement of most of the same parts.

I recently had this P0125 pop up after replacing my downstream O2 sensor without any prior indication from OBDII. The connectors on both O2 sensors can get a lot of dirt/sand stuck in them preventing a good connection. On the first page someone mentioned the P0125 was caused from an open/short connection. I'd double check the connector to ensure the tab on the connector is engaged indicating a fully seated O2 sensor. If one is positive the connection is good double check the harness by reading the wires out with an ohm meter.

Olaf so your issue was the blue wire on the 02? What do you mean by sheathing was preventing a connection? -Thread resurrected.

 

[98 SNAKE EATER]

Threw a PO125 earlier tonight

Tried clearing it on the go, but it came back instantly

Pulled over, shut off the engine, then cleared it with the igintion on and it went away, but came back about 10 minutes later

Data stream shows the ECT not exceeding 188*, so I'm guessing the T-Stat might be stuck open

Fan clutch feels normal (modified blue), but I'm gunna start her up tomorrow with the cap off to see if the coolant flows when cold

 

[secretasiansam]

Threw a PO125 earlier tonight

Tried clearing it on the go, but it came back instantly

Pulled over, shut off the engine, then cleared it with the igintion on and it went away, but came back about 10 minutes later

Data stream shows the ECT not exceeding 188*, so I'm guessing the T-Stat might be stuck open

Fan clutch feels normal (modified blue), but I'm gunna start her up tomorrow with the cap off to see if the coolant flows when cold

I just got a p0125 as well, but I cut my 02 sensor bungs off and have the old 02 sensors wired onto the exhaust. I'm waiting on new 02 bungs to arrive to put new 02 sensors in. All my reading points to bad 02 sensors triggering the p0125.

 

[98 SNAKE EATER]

I just got a p0125 as well, but I cut my 02 sensor bungs off and have the old 02 sensors wired onto the exhaust. I'm waiting on new 02 bungs to arrive to put new 02 sensors in. All my reading points to bad 02 sensors triggering the p0125.

What is your ECT reading?

This morning I did a cold start with the cap off and the coolant instantly started rising

No bubbles, just kept rising until I capped it as it started spilling over in less than 45 seconds

Drove around for about 20 minutes and she threw the PO125 again

Data stream showed she never went above 188*

Stopped, cleared the code and set the hand throttle at 3,000 RPM's for about 5 minutes

Highest ECT got to was 190*

Gunna hit her with a temp gun on my next drive just to rule out a faulty temp sensor, but I'm pretty sure its just a stuck T-Stat

 

[secretasiansam]

What is your ECT reading?

This morning I did a cold start with the cap off and the coolant instantly started rising

No bubbles, just kept rising until I capped it as it started spilling over in less than 45 seconds

Drove around for about 20 minutes and she threw the PO125 again

Data stream showed she never went above 188*

Stopped, cleared the code and set the hand throttle at 3,000 RPM's for about 5 minutes

Highest ECT got to was 190*

Gunna hit her with a temp gun on my next drive just to rule out a faulty temp sensor, but I'm pretty sure its just a stuck T-Stat

It just came on as I pulled into work this morning. I'll check the scan gauge on the way home.

 

[98 SNAKE EATER]

Update?

 

[secretasiansam]

Update?

I haven't gotten above 180 on my 6 mile drive to/from work. Today has been the warmest at 50*.

 

[98 SNAKE EATER]

OK, a little update for me then....

Temp gun checked out fine and the readings were pretty much on par with what the data stream was showing..

Picked up a new T-Stat from the dealer yesterday and threw it in earlier today.

The old one didn't appear to be stuck, but it could've snapped closed when I was trying to wiggle it out from the housing (plan on bench testing it when I get a chance).

Unfortunately, it didn't fix my issue

Upon start up with the new T-Stat, there was no flow or bubbles, so that's good, but the temps are still staying too cold

I set the hand throttle to about 2500 RPM's and burped the system, but the temps never went above 188* while standing.

Drove around HARD for a few miles, but it never went above 190* and would creep down to around 179*

Fan clutch appears to be functioning the same as when I first did the fluid mod.

I get the usual cold start roar and it moves so much air that it suck/spins my JDM fan before settling down after about 40 seconds or so


On the way home from the shop, I kept the data stream going and she threw a few more codes:

PO125 (Insufficient Coolant Temp for Closed Loop)
PO130 (O2 Sensor Circuit Bank 1 Sensor 1)
PO133 (O2 Sensor Slow Response Bank 1 Sensor 1)
PO135 (O2 Sensor Heater Circuit Bank 1 Sensor 1)
PO171 (System Too Lean Bank 1)

At around ~181*, the system seemed to toggle back and forth between open and closed loop

Gunna check the O2 connection when I get a chance cause I had loaded it up with dielectic grease years ago

Not looking forward to replacing it if I have to cause the nuts are quite horrid

 

[98 SNAKE EATER]

OK, I finally got a chance to crawl underneath and found a broken wire on the pigtail

I really hope thats the only problem cause by the looks of the nuts on the sensor, it's not gunna be fun to replace

Anyone have a part number for an OEM pigtail?

 

[98 SNAKE EATER]

OK, another update on this.....

Picked up a pigtail on EBay and spliced it in early this morning

Started her up for the first time in a couple of weeks, plugged in my scanner and surprisingly by the time it connected to the live data stream, it was already in closed loop, which was kinda strange cause she hadn't gotten up to temp yet

This was probably just over a minute after starting

Went for a drive and kept the data stream running, but she was still running cold (Highest ECT 186*/Highest ICT 84*)

Don't wanna jinx it, but I've done 3 drive cycles with about ~80 miles and no codes so far

 

[landtank]

P0125 has typically been a heater circuit failure in the front O2 sensor. Repairing that broken harness likely took care of the problem.