Need help! P0171, P0175, P0118, P0113, and P0102 codes.

[walkgiam2]

Hello everyone,

I have a 2006 lx470 with about 200k on it. I have gotten a intermittent P0171 and P0175 codes couple times at random. After the second time I replaced the MAF with a new OEM Hitachi based off of research done on here. Unfortunately that didn't fix the issue but it does run even smoother so at least it didn't feel like a waste. P0171 came back a few weeks later. I hooked up techstream and it showed P0171 and pending P0175. Cleared the codes and drove it around and they came back after about a mile along with all of the other codes. It also had a noticeable stumble from a stop which it had only done that one time before.

So far I have checked the grounds and power on the ECT connector and MAF sensor and they seem to be good.
My guess is it could still be a frayed wire somewhere.

Hopefully someone else might have a suggestion on what to check next.

P0172 and P0175 Rich bank 1 and 2
P0118 engine coolant temp sensor 1 circuit high
P0113 intake air temp sensor 1 circuit high
P0102 Mass air flow circuit low

 

[white_lx]

It seems the rich codes are a result of the electrical problem in the 3 sensors, resulting in incorrect mass flow and air temperature. What are the values; were you able to read those at idle?

The only thing the 3 sensors have in common is the ground. I believe it is a brown wire. The intake air temp and mass flow ground are actually the same pin on the MAF. The coolant sensor is close by and shares the same ground. That's where I would start: Inspect the signal ground wires and back-probe the ground and measure with a volt meter while doing a wiggle test of the wires and at the connectors.

 

[walkgiam2]

When i was checking values on techstream I was checking to 02 sensors by changing the fuel trim. I thought that's what it might be at the time. Ill have to hook it back up and do some more checking.

I believe you are correct about it being a electrical problem. The back probe kit should be here tomorrow. Hopefully it won't take too much wiggling to find a break in the wire.

 

[white_lx]

When i was checking values on techstream I was checking to 02 sensors by changing the fuel trim. I thought that's what it might be at the time. Ill have to hook it back up and do some more checking.

I believe you are correct about it being a electrical problem. The back probe kit should be here tomorrow. Hopefully it won't take too much wiggling to find a break in the wire.

This is assuming all the codes that you listed are current? Rich/Lean is determined from the mass flow and intake temperature. If these readings are not correct, the ECM will report lean/rich even if it isn't.

When you hook up the scan tool, check the MAF and intake temperatures. Intake temperatures should be around ambient, maybe a bit higher if the engine bay is hot. The MAF should read around 5 gram/s (slightly below) at idle of 650-700 rpm.

Once those values are reading correctly, the rich codes would be next (if they are still existing). What are your current fuel trims?

 

[walkgiam2]

All the codes were current as of yesterday and today. I brought techstream back up and everything was reading correctly. I tried to get it to give me a code again with no luck. I used my multimeter and gave everything a good wiggle test with no change. Im going to drive it a good bit tomorrow so maybe it'll come up again.

It still seems like a ground issue, just not luck catching it yet.

Thank you for your help BTW

 

[white_lx]

I tried to get it to give me a code again with no luck.

Check if under those conditions the fuel trims are OK and the rich codes will not return. In that case you can forget about them and just focus on the other 3 codes.

Also a suggestion to check the MAF connector. I have read here that they are sometimes not making good contact, although that would not explain the coolant sensor code in your case.

The ground wire runs through junction connector J17 which is located behind the glovebox. That connector is another candidate for bad continuity of the ground back to the ECM, although not very likely.

 

[walkgiam2]

Im not terribly concerned with the rich codes since I think im only getting those from intermittent ground issues making the computer dump fuel.

I did wiggle the MAF connector as well and had no changes.

One thing I did notice is that if I check the grounds to the battery with the key off I would get a constant continuity tone. But with the key on it would beep quickly then start showing ohms readings. I don't know if that really means anything but I found it interesting .

 

[walkgiam2]

I missed that you mentioned the J17 connector. That's a great idea to check next.

 

[white_lx]

I missed that you mentioned the J17 connector. That's a great idea to check next.

Would only suggest doing this when it is acting up, otherwise diagnosis willl be hard. Also start with checking everything under the hood.

One thing I did notice is that if I check the grounds to the battery with the key off I would get a constant continuity tone. But with the key on it would beep quickly then start showing ohms readings. I don't know if that really means anything but I found it interesting .

Make sure you don't use the continuity check, but check for voltage (mili-volt) at the sensors grounds. You want to make sure they are not becoming disconnected from the sensor ground back to the ECM. The error codes you presented will only show if there is a discontinuity in the ground path as it will raise the voltage at the sensor grounds to the reference voltage which is around 5V. Sensors grounds and vehicle ground are distinct to prevent interference. Btw. technically, a failed ECM could also be the culprit, but let's assume for now it is not.

 

[2001LC]

I'll note:

We see many different electrical gremlins. Due to water entering the cabin down "A" pillars.

1. Number one cause is when windshield replaced. Open rivet or rust holes under molding or poor seal (black ploy glue) around windshield.
2. Number two cause: Sun roof drains clogged. Which can also run down "A" pillars.

If water entry has accrued, and allowed for extended period. Oxidation builds up on contacts. Then issues may then persist, even after water dries up and or holes plugged.

Also, watch out for any after market wiring and or rodent chew damage.

 

[walkgiam2]

Hello, after a day of driving I did find something interesting.

In the morning while it was still coolish the 02 sensors and fuel trims were pretty spot on with each other. The short term fuel trim was 0 to 0.8 and the long term was -1.6. After it got well into the 90s I noticed on my cheap scan gauge that bank 2 sensor 2 voltage was diffrent at idle and the fuel trims were different.

I got home and hooked up techstream and used the fuel trim tool. At idle it was showing the weird voltage but everything leveled out when I used +/- 12.5 fuel

I do know that the previous owner replaced both 02 sensors on the passenger side bank 2 with the upstream one being a oem denso and the downstream being a parts store one.

I am fairly certain the driver side bank 1 02 sensors are original and at 200k its probably not a bad idea to replace them.

And to 2001LCs point the windshield that was in it when I got it was installed wrong and leaked on the A pillars. I had the windshield replaced correctly about 6 months ago and everything has been good.

I can see where where water had gotten in but I don't see where it ever got on the ECU. Not saying it didn't I just couldn't find anything even after pulling the ECU connectors and checking for corrosion. Ill add a picture in a separate reply.

Do you think it is possible that a dying 02 sensor can cause some weird grounding issues with the common ground between all of the sensors?

 

[walkgiam2]

Corrosion picture

 

[white_lx]

In the morning while it was still coolish the 02 sensors and fuel trims were pretty spot on with each other. The short term fuel trim was 0 to 0.8 and the long term was -1.6. After it got well into the 90s I noticed on my cheap scan gauge that bank 2 sensor 2 voltage was diffrent at idle and the fuel trims were different.

Secondary oxygen sensor readings mean nothing. They just randomly vary all the time, slowly.

Your + and - trim tests show perfect nominal behavior for primary and secondary sensors:

• no trim: Primary A/F: 3.3V (stoich), Secondary O2: between 0 and 0.9V (between rich and lean) -> normal behavior
• -12.5 trim: Primary A/F: 3.77V (lean), Secondary O2: 0.05V (lean) -> normal behavior
• +12.5 trim: Primary A/F: 2.4V (rich), Seondary O2: 0.85V (rich) -> normal behavior

So, this is all normal. I would not replace any of the sensors. Also, +/- 10% fuel trims will not set a rich/lean code.

Do you think it is possible that a dying 02 sensor can cause some weird grounding issues with the common ground between all of the sensors?

The secondary sensors do share the sensor grounds, but based on previous findings, I would move on from the O2 sensors.

Your Techstream data does show the initial intake temperature as 37F !! ? I believe it is the initial intake temp, but part of it is cut-off. Is that correct for GA today? Or do you maybe have one of the bypass modules for the secondary air injection? That would explain the strange sensor readings. These modules are designed to bypass air intake temperatures and coolant temperatures during start-up. If that is the case, that would explain all the issues you are having.

 

[walkgiam2]

Lol I wish it was 37F in GA right now.

I do have the hewitt tech gen 1 bypass kit installed. Its been on there about 2 years and hasn't given me any problems before. Not to say it couldn't. I only ruled it out because of the ECT sensor throwing a code. And the codes only showed up after ive driven it around and its warmed up. My thinking with that is that if just the MAF had lost signal and not the ECT then it was probably the bypass. And it would throw a code closer to startup.

I will need to hook up techstream again tomorrow and check the initial intake temp reading. I didn't notice that at all. Thank you for pointing that out.

 

[white_lx]

Lol I wish it was 37F in GA right now.

I do have the hewitt tech gen 1 bypass kit installed. Its been on there about 2 years and hasn't given me any problems before. Not to say it couldn't. I only ruled it out because of the ECT sensor throwing a code. And the codes only showed up after ive driven it around and its warmed up. My thinking with that is that if just the MAF had lost signal and not the ECT then it was probably the bypass. And it would throw a code closer to startup.

I will need to hook up techstream again tomorrow and check the initial intake temp reading. I didn't notice that at all. Thank you for pointing that out.

So, it could be a failing of the Hewitt module. Either the connectors, the wiring, the hardwire strain relief in the module or the relays in the module. That would explain the symptoms of MAF, IAT and rich codes. Maybe the ECT code is a coincidence? Or maybe the ECM is confused by the variability in different signals and sets that code in error? It might be difficult to diagnose without it being a current code. (For a moment I was also thinking of Hewitt modules, for 2008 Lexus models, that do have ECT sensor bypass).

Forum members have reported MAF/IAT problems in combination with older Hewitt modules here in the past. The one I personally handled had wires potted into the module. I'm wondering if they were soldered to a board inside. Soldered wires makes them brittle. If they are indeed soldered, it would be better if they were crimped. You could try a wiggle test near the wires leaving the module.

 

[walkgiam2]

Not as far as I am aware. This kit only has a signal wire and plug for the MAF sensor. Its also entirely possible for it to do something weird with interrupting the ground if the module is dying.

I found some posts on a tunda forums about the hewitt tech giving rich codes after a couple years. Looks like it is the most likely culprit after all. Im going to drive it around with the kit still plugged in and if I get the code again I'll swap the MAF plug back to the factory one and see what happens.

This is the kit I have.

Hewitt-Tech Gen 1: Secondary Air Injection System Bypass Kit (Plug & Play)

Gen 1 (V36H) SAIS Bypass Kit is compatible with most 2005 - 2007 Toyota / Lexus Trucks & SUVs. It enables you to clear the Check Engine Light, Limp Mode and error codes related to mechanical SAIS faults. P1441 P1442 P1444 P1445 P2440 P2441 P2442 P2443 P2445 P2447

hewitt-tech.com

Thank you again for your help!

 

[2001LC]

I really don't understand why anybody wires in devices to bypass anti pollution.
I'm done here!