New here, hello! And Some Troubleshooting Questions (VSC/CEL) (1 Viewer)

[jrw182]

Hello, I'm new to this forum but not new to forums in general so I wanted to lead in by saying I have done a lot of research on these lights so I'm not just posting blindly without doing some digging on my end first. I understand these lights can come on for almost any reason so I'll try to provide some details.

I recently bought a 2004 GX470 with 220k on the odo. Body is overall good with some dings, but it is 20 years old after all. The underside is great being a California car, it has most likely only seen pavement It's pretty sound from what I can tell (besides the VSC/CEL light), but the previous owner had the timing belt, water pump, valve cover gasket done on schedule, other maintenance as scheduled, and the AC/servos replaced, dash replaced, etc.. The air suspension has been removed also.

I did try the gas cap replacement first off, cleared the codes, then my next time driving the lights came back on after around 5 minutes so no dice there.

Codes
I ran a full health check with Techstream and came up with the following:
P0031(Current) - O2 Sensor Bank 1 Upstream
P0420(Pending) - Catalyst System Below Efficiency Bank 1

Also
C1201- Engine Control System
C1223- ABS Control System Malfunction (No abs light on dash though)
C1246- Master Cylinder Pressure Sensor (Brakes feel as if they operate normally)
C1340- Open Circuit in Center Differential (I have operated the diff lock on and off and it does function)

Along with these I recorded the long and short term fuel trim with my scanned and I'm getting a -3% on the LTFT for both banks, which indicates the computer seeing a rich environment, correct?

Plan
Since the gas cap didn't work I'm thinking jump right in and replace both upstream O2 sensors with OE (Denso) units? I understand exhaust leaks can be common around the manifold, but I haven't heard anything that definitively sounds like an exhaust leak, I'd think one big enough to throw off the O2 sensor would sound very obvious.

As for the negative fuel trim I checked the air filter and it's clean, next step maybe pull the MAF sensor and clean if needed?

I don't know where to start on the abs codes, since no dash light is on I'm assuming the abs is working, but something lit those codes at one point. Maybe just start with a wiring/sensor check and go from there?

I'd appreciate any advice on something glaringly obvious I'm missing, I have also checked all the fuses with a multimeter and none are blow. Thanks!

 

[greatdivider]

P0031 is for the heater circuit, nothing to do with fuel mixture. A 3% fuel trim is completely normal. Codes won't set until its like + or- 20% for an extended period of time (depends on manufacturer). You can measure the resistance of the heating element in the sensor, as well as check power and ground for it at the engine harness side. 99% of the time it's a bad sensor causing this.

I would clear the P0420 and just see if it comes back. Lots of possible causes but if you have no exhaust leaks, it's likely a failing catalytic converter. You could graph the O2 sensors and see what they look like. Both banks should look the same. If the cat is failed, the B1S2 sensor will switch between high and low voltage mirroring the upstream sensor.

C1202, C1223 just set because of the other codes. I'd clear the ABS codes and wait for something to return

 

[jrw182]

P0031 is for the heater circuit, nothing to do with fuel mixture. A 3% fuel trim is completely normal. Codes won't set until its like + or- 20% for an extended period of time (depends on manufacturer). You can measure the resistance of the heating element in the sensor, as well as check power and ground for it at the engine harness side. 99% of the time it's a bad sensor causing this.

I would clear the P0420 and just see if it comes back. Lots of possible causes but if you have no exhaust leaks, it's likely a failing catalytic converter. You could graph the O2 sensors and see what they look like. Both banks should look the same. If the cat is failed, the B1S2 sensor will switch between high and low voltage mirroring the upstream sensor.

C1202, C1223 just set because of the other codes. I'd clear the ABS codes and wait for something to return

Thanks for the response, give me something to look into. Here’s a couple screenshots from the same time stamp.

B1, S1 vs S2

B1S1 vs B2S1

If I’m understanding what you said correctly since B1S1 vs B2S1 look similar, but B1S1 vs B2S1 are not a O2 sensor would be worth investigating? All this being said under the fact of one timestamp of the graph of course.
That being said, I will be checking out the sensor this weekend, and testing for exhaust leaks.

 

[jrw182]

Even though I couldn’t hear it, after doing a pressure test I found a crack on the cylinder 1 exhaust manifold. Now to decide whether to replace with oem, DT long tube headers, or live with it till it does become pretty obvious there’s a manifold leak? I’m fairly handy, but I know the headers on this aren’t an easy task. I think it’s time to call around and get some labor estimates.

 

[Rednexus]

You probably need new upstream and downstream O2 sensors. They are usually the cheapest on Rock Auto. You can use universal Denso O2 4-wire sensors for the downstream ones. The upstream sensors will need to be vehicle-specific, and they aren't cheap ($100-150 each).

Regarding the manifolds, every GX470 will eventually the manifold tick. Since you are also here in the Show-Me State, we have the freedom of no emissions checks. I installed a set of Doug Thorley long tubes on my VVTI GX and it's an awesome power upgrade. I sold the two upstream cats for $600, which paid for most of the headers. The DIY install took me around 22 hours. It's probably a bit easier on your non-VVTI engine, but I can easily see the labor being 12-18 hours, if you can find someone who is willing to do the job. It's really a pretty terrible job, but worth it.

 

[jrw182]

You probably need new upstream and downstream O2 sensors. They are usually the cheapest on Rock Auto. You can use universal Denso O2 4-wire sensors for the downstream ones. The upstream sensors will need to be vehicle-specific, and they aren't cheap ($100-150 each).

Regarding the manifolds, every GX470 will eventually the manifold tick. Since you are also here in the Show-Me State, we have the freedom of no emissions checks. I installed a set of Doug Thorley long tubes on my VVTI GX and it's an awesome power upgrade. I sold the two upstream cats for $600, which paid for most of the headers. The DIY install took me around 22 hours. It's probably a bit easier on your non-VVTI engine, but I can easily see the labor being 12-18 hours, if you can find someone who is willing to do the job. It's really a pretty terrible job, but worth it.

Thanks for the input! I actually scrolled through your build post awhile back and saw how much of a dog the headers were, not to say impossible though obviously. Really nice job on your GX though. That’s a good point as well on selling the cats to recoup a little money.

Last night I came across a slight leak on the radiator (driver side lower), didn’t catch it at first because it wasn’t leaking enough to leave a spot on the ground. Nonetheless, OE Denso unit on the way as well as a new cap and Toyota coolant. Going to handle this first, check out to ensure the trans-cooler didn’t get breached, then move on to what I’m looking to do with the exhaust manifold.

 

[jrw182]

Got the new Denso radiator in from RockAuto. I did see some comments about the parts store Denso radiators being slightly different than the OEM Denso radiator, and that is true, but everything lines up perfectly and it seems just as sturdy by visual inspection.
Had the old one already pulled and the new placed and filled in around an hour. The biggest shock for me was the Toyota SLL Coolant, that ran me $37 a gallon… for an already premixed product.
I’m not sure how much trans fluid was lost in the swap, I believe it supposed to be very small, but I did refill at least what came out of the send line.
That being said what I collected was pretty dark, so I think I’m going to do a full fluid/ screen/ clean pan based on what I’ve seen the consensus on here. I don’t know the previous owners service history on trans fluid swap.

 

[jrw182]

I was a little concerned about changing the transmission fluid due to the mileage and not knowing the previous history of transmission service, but based on the sample I pulled out when changing the radiator it didn’t smell burnt or look too dark so I proceeded.
I did run into a complication, my GX is different than what I’ve seen as I have 3 cats (which is one of the layouts on the parts diagram), and the Y pipe crosses the drain pan. I don’t believe there’s room to get the pan out without pulling the mid pipe. The connector pipe nuts came loose on one side, but felt seized on the other side, I didn’t want to risk breaking a stud so I made the call not to drop pan.
Proceeded to drain out 3 quarts, maybe a tad low, Pump in 3.25 qts. Then do the exchange method by pumping out 2qts at a time through the send line and pump back in just a tad more than I got out. Ended up doing 16qts in total. On the level check I got out right around 10oz. so I believe I got it right.