Superfast1

I have been taking great care of my 97 LS400 so it's in great shape & runs silky smooth, however every now & then, it would threw the above code. I've checked the long-term fuel trims w/ the OBDII scanner & they both at -18% or more (or less I should said as it being negative), however I can get both fuel trims back to +/- 0% by wiggled some of the 5 wires in the back of the MAF's connector. Both fuel trims would stay at around +/- 0% for a few months then the error code popped up again. I think I have an intermittent at the connector's so just ordered a new one & it's in the mail. What do you think?

By the way, while I had the scanner hooked up this morning, I've noticed the ECT at cold is at 54 deg F, which is the same as the outside temp, however the ECT temp moved up to 100 deg within 1 min after a cold start then reached 180 after 4 min or so. I've replaced the ECT sensor last year w/ the Duralast sensor purchased from Autozone. Is it possible the engine can heat up the coolant that quick? It just seems too quick for me. What's your take on this?

RA40

iTrader: (6)

My suggestion would be to also check-replace the bank 1 O2 sensors.

Roughly after 2 miles of driving the engine temp gauge is at normal operating temp/just above the second line. The car will be blowing heat from the vents by the time 1 mile is reached. It may be up to temp reasonably quick.

Superfast1

All 4 O2 upstream & downstream sensors had been replaced couple years ago. I've also checked them yesterday & they're functioning properly (upstream sensors on both banks swing between .1 to .9 V).

RA40

iTrader: (6)

Good, one less potential contributor to an air fuel mix error. Will see what the new connector brings.

Superfast1

I've finally got my P0172 Rich Condition on Bank 1 fixed after a long while of troubleshooting. As suspected, I had a bad MAF sensor's connector (not a bad MF's connector but in my case, you can say that too). It's a 5-pin connector & 1 or more pins were lose which caused the intermittent & lost connection w/ the mating connector from the MAF sensor. As stated, I could wiggle the wires in the back of the connector to get the LTFT's on both banks to change from -18% or lower (rich condition) back to 0%, however due to the vibration in the engine compartment when the car is running & after a few months, the connection would opened up again & caused the car to run rich & triggerred the Check Engine light. Who would have thought this rich condition was caused by an intermittent inside the connector as I have brought the car to a number of auto mechanics & none of them were able to diagnose it correctly. Anyway, I bought another connector, cut, spliced & soldered the 5 wires & now the car runs as new w/ both LTFT's right at around 0%, a perfect air/fuel ratio of 14.7:1. I had this repair done a few weeks ago but wanted to complete the drive cycle for all the emission monitors & also wanted to make sure it's the real fix before I report back. I'm happy to say it is a real fix so for those of you that run into the same or similar problem I had, use the OBDII scanner. If you don't have one, buy one as it's a valuable diagnostic tool & it will pay for itself in one use & here's how you troubleshoot: With the car running (after it has been warmed up), look at the LTFT's & wiggle the connector(s), wires or run your hand all over the engine's components (it's hot so be careful) & see if they change. If you have a lean condition instead, do a visual inspection and/or run your hand over all the vacuum hoses as you may have a leak at one of the hoses. Good luck.

Legender

Thanks for the update. That was a good and I'm sure difficult find. Thank you for sharing your results and working to confirm the solution. Posts like this are what make this site so valuable to so many. I recently, last week, just got a P0172 pop up on my 98 and besides the standard 02 sensor check I'll look at this possibility also.

Superfast1

Legender- Yeah, I don't like to leave post w/ non-closure then it would be useless. I'm also the type that once I've started something, I have to find the solution or a way to get it done. I guess it's in my DNA. Hope you'll find yours too. Let me know if I can help.