Diagnosing catalytic converters.

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Tlhfirelion

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Hello everyone. I have an 01 Toyota Sequoia Limited, 250,000 miles, 4.7 L V8. Running good but have had some CEL's as of late. Long story short, I replaced all 4 O2 sensors as it appeared they were the originals, or at least very old and I was getting codes saying it was them. Fast forward a couple months and I now have the P0420 code. A temp gun scan of the cats after letting the vehicle run for 15 minutes and up to operating temp showed the following temp readings.

Cat 1- into cat temp 300 degrees and outgoing temp is 375.

Cat 2- Into cat is 298 degrees and outgoing temp is 310.

Now it's VERY cold here today, in the teens and I started the vehicle cold, let it run for 15 minutes so I assume that's good enough for this temp test. I can't be sure but I think I've gotten a hint of rotten egg smell from the exhaust, but if it's there, it's random and faint. This engine doesn't get the best MPG's at around 14-15 on the highway for most folks, and I average 11.8. I have felt some SLIGHT sputtering when cruising down the highway, very random, very slight. The CEL has come on and gone off a few times on its own and not its staying on.

The vehicle runs good, Idiles smooth, cruises fine, and has all new Denso 02 sensors, so aside from the cats, I don't know what else to check.

Am I headed down the right path or am I missing something? Thank you in advance for your assistance.

* I just reran the codes and I'm really confused. The p0420 is not there active or pending, and now it shows a p0171 and p0174. Fuel pump maybe?
 
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Try cleaning the MAF sensor, check for obvious vacuum leaks eg cracked, loose or broken hoses, check MAF to TB hose (the big accordion one) for cracks carefully.
Post fuel trims if you can, you have lean code for both banks.
 
I just checked the MAF sensor. I checked my log book and I had replaced it with a hitachi one in Jan of 2017. Visually it looks very clean, shall I still clean it? I've looked at all the hoses and I can't find anything obviously leaking aside from the fluid in the power steering lines. They both seem to seep but have been that way awhile. I am u sure if I can post fuel trims, I only have the OBD fusion app and Bluetooth connector. I'll examine the TB hose. Thank you for your assistance.
 
Some engines foul their MAF sensors. Others leave them clean, and using a cleaning spray only risks messing up the sensor.

P0171 and P0174 codes suggest that there is a vacuum leak after the MAF, not that the MAF is reporting wrong values.
 
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Ok, so this is about as much info as I know how to get off this app. Hopefully you know what you're looking at because I don't know much about it. Thank you.

Diagnostic Report


Created by OBD Fusion - OCTech, LLC www.obdsoftware.net

Date: 1/19/2019 6:24:47 PM

VIN: Not Available

Monitor Status Report


Name Continuous Available Complete
Misfire Yes Yes Yes
Fuel System Yes Yes Yes
Components Yes Yes Yes
Catalyst No Yes Yes
Heated Catalyst No No No
Evap System No Yes No
Secondary Air System No No No
AC Refrigerant No No No
Oxygen Sensor No Yes Yes
Oxygen Sensor Heater No Yes Yes
EGR System No No No

MIL Off
Number of Confirmed Codes: 2
Readiness Standard: None

This vehicle is not ready for emissions testing.

Reason
Confirmed trouble codes have been detected
Trouble Code Report


ECU Code Type Status Description
10 P0171 PowerTrain Confirmed System Too Lean
10 P0174 PowerTrain Confirmed System Too Lean

Mode $01 - Powertrain Diagnostic Data


PID Description Value Units
SAE 0x03 Fuel system 1 status 1
SAE 0x03 Fuel system 2 status 1
SAE 0x04 Calculated load value 19.61 %
SAE 0x05 Engine coolant temperature 156.2 F
SAE 0x06 Short term fuel % trim - Bank 1 0 %
SAE 0x07 Long term fuel % trim - Bank 1 21.88 %
SAE 0x08 Short term fuel % trim - Bank 2 0 %
SAE 0x09 Long term fuel % trim - Bank 2 31.25 %
SAE 0x0C Engine RPM 704.5 RPM
SAE 0x0D Vehicle speed 0 MPH
SAE 0x0E Ignition timing advance for #1 cylinder 10 deg
SAE 0x0F Intake air temperature 82.4 F
SAE 0x10 Mass air flow rate 0.84 lb/min
SAE 0x11 Absolute throttle position 14.12 %
SAE 0x13 Location of oxygen sensors 51
SAE 0x14 O2 voltage (Bank 1, Sensor 1) 0.02 V
SAE 0x14 Short term fuel trim (Bank 1, Sensor 1) 0 %
SAE 0x15 O2 voltage (Bank 1, Sensor 2) 0.02 V
SAE 0x15 Short term fuel trim (Bank 1, Sensor 2) 99.22 %
SAE 0x18 O2 voltage (Bank 2, Sensor 1) 0.02 V
SAE 0x18 Short term fuel trim (Bank 2, Sensor 1) 0 %
SAE 0x19 O2 voltage (Bank 2, Sensor 2) 0.02 V
SAE 0x19 Short term fuel trim (Bank 2, Sensor 2) 99.22 %
SAE 0x1C OBD requirements to which vehicle or engine is certified 1
Aux 0x00 Input voltage read by the scan tool 13.8 V

Mode $02 - Freeze Frame


PID Description Value Units
0x02 Freeze frame DTC P0174
0x03 Fuel system 1 status 2
0x03 Fuel system 2 status 2
0x04 Calculated load value 56.47 %
0x05 Engine coolant temperature 183.2 F
0x06 Short term fuel % trim - Bank 1 4.69 %
0x07 Long term fuel % trim - Bank 1 34.38 %
0x08 Short term fuel % trim - Bank 2 8.59 %
0x09 Long term fuel % trim - Bank 2 34.38 %
0x0C Engine RPM 1469.5 RPM
0x0D Vehicle speed 44.12 MPH
0x0F Intake air temperature 64.4 F

Mode $05 - Oxygen Sensors


Sensor Available
Bank 1 - Sensor 1 Yes
Bank 1 - Sensor 2 Yes
Bank 1 - Sensor 3 No
Bank 1 - Sensor 4 No
Bank 2 - Sensor 1 Yes
Bank 2 - Sensor 2 Yes
Bank 2 - Sensor 3 No
Bank 2 - Sensor 4 No

Sensor Description Value Minimum Maximum Units Result
Bank 1 - Sensor 1 TID $03 - Low sensor voltage for switch time calculation(constant) 0.4 0 1.275 V Pass
Bank 1 - Sensor 1 TID $04 - High sensor voltage for switch time calculation(constant) 0.55 0 1.275 V Pass
Bank 1 - Sensor 1 TID $07 - Minimum sensor voltage for test cycle (calculated) 1.275 0 1.275 V Pass
Bank 1 - Sensor 1 TID $08 - Maximum sensor voltage for test cycle (calculated) 0 0 1.275 V Pass
Bank 1 - Sensor 1 TID $31 - Manufacturer Defined 10.2 0 10.2 sec Pass
Bank 1 - Sensor 1 TID $32 - Manufacturer Defined 10.2 0 10.2 sec Pass
Bank 1 - Sensor 2 TID $07 - Minimum sensor voltage for test cycle (calculated) 1.275 0 1.275 V Pass
Bank 1 - Sensor 2 TID $08 - Maximum sensor voltage for test cycle (calculated) 0 0 1.275 V Pass
Bank 2 - Sensor 1 TID $03 - Low sensor voltage for switch time calculation(constant) 0.4 0 1.275 V Pass
Bank 2 - Sensor 1 TID $04 - High sensor voltage for switch time calculation(constant) 0.55 0 1.275 V Pass
Bank 2 - Sensor 1 TID $07 - Minimum sensor voltage for test cycle (calculated) 1.275 0 1.275 V Pass
Bank 2 - Sensor 1 TID $08 - Maximum sensor voltage for test cycle (calculated) 0 0 1.275 V Pass
Bank 2 - Sensor 1 TID $31 - Manufacturer Defined 10.2 0 10.2 sec Pass
Bank 2 - Sensor 1 TID $32 - Manufacturer Defined 10.2 0 10.2 sec Pass
Bank 2 - Sensor 2 TID $07 - Minimum sensor voltage for test cycle (calculated) 1.275 0 1.275 V Pass
Bank 2 - Sensor 2 TID $08 - Maximum sensor voltage for test cycle (calculated) 0 0 1.275 V Pass

Mode $06 - On-Board Monitoring


Component Description Value Minimum Maximum Units Result
Component Id $01 TID $01 - Manufacturer Defined 10 N/A 128 Pass
Component Id $02 TID $01 - Manufacturer Defined 30 N/A 128 Pass
Component Id $01 TID $02 - Manufacturer Defined 255 76 N/A Pass
Component Id $02 TID $02 - Manufacturer Defined 108 64 N/A Pass
Component Id $03 TID $02 - Manufacturer Defined 1 N/A 26 Pass
Component Id $01 TID $04 - Manufacturer Defined 6496 3277 N/A Pass
Component Id $02 TID $04 - Manufacturer Defined 7470 3277 N/A Pass
Component Id $10 TID $04 - Manufacturer Defined 6496 3277 N/A Pass
Component Id $20 TID $04 - Manufacturer Defined 7362 3277 N/A Pass
Component Id $01 TID $08 - Manufacturer Defined 184 184 N/A Pass

Mode $09 - Vehicle Information


General Information

Description Value
Vehicle Identification Number Not Available
Calibration ID - $10 30C10000
Calibration ID - $10 10C20002
Calibration Verification Number Not Available
 
How long did this engine run when you got these readings? Engine coolant temperature 156.2 F

Edit: Never mind I see whats going on now.
 
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I don't have a fuel pressure gauge and I'm not quite sure what I'm doing there. Any advice on how to do so? Thank you.
 
I don't think these have a test port so you must T into the fuel pressure regulator, member Clinebarger might know the exact procedure, PM him.
If that is the way I think it is you are probably better off using a dealer or garage for this test. My kit has a banjo adapter and bolt for some engines but I haven't had chance to use it.
Did you check the big hose from the MAF to the throttle body yet?
 
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Most Toyota products don't have a test port/schrader & this vehicle is no exception. While I agree with Trav to take it to a dealer/garage for testing......There are some workarounds without spending a fortune.

1/8" Tapped 12mm-1.25 Banjo Bolt.....HERE
1/8" NPT x 1/4" Schrader flare............HERE
R-12/R-22 Refrigerant Gauge Set.......HERE
***You can probably find a good used set of gauges at a local pawn shop!! Or even a really cheap Chicom set will work a couple times??
 
A quick & dirty way to eliminate low fuel pressure as a cause of the Lean Codes.....

Monitor these 4 PID's while performing this test......
SAE 0x06 Short term fuel % trim - Bank 1 0%
SAE 0x07 Long term fuel % trim - Bank 1 21.88%
SAE 0x08 Short term fuel % trim - Bank 2 0%
SAE 0x09 Long term fuel % trim - Bank 2 31.25%

*Thoroughly warm-up the engine
*On level concrete/asphalt, Set the E-Brake, Block BOTH drive wheels really well (With Wheel Chocks preferably) And firmly press the brake pedal with you left foot.
*Put the transmission in Manual Low/1st Gear.
*Press the accelerator 'til you reach @1900-2200 RPM (Your loading the engine against the Torque Converter)
*Keep this test to under 2 minutes to avoid possible transmission overheat, IF you can monitor trans temp.....DO NOT exceed 210°F.

IF the fuel trims start to correct........
*Short Terms go Negative.
*Long Terms start to correct/trend down.
Your fuel pressure is likely OK!!!

IF the fuel trims get worse (More Positive corrections), I would definitely check the fuel pressure before proceeding!
 
On lean condition codes i start with the fuel filter then work my way to the airbox and ducting then onto vacuum leaks. Could be as simple as a hose or the worst a cracked intake or gaskets.
 
I had to step away from this project for a day, I'll be back! Thank you gentlemen for your assistance.
 
That temp reading on cat 2 certainly looks like its bad, or at least not performing as well as the one on the other side. Probably enough to set a code. If you have a scan tool with the ability to graph live data, look at the O2 sensor graphs (front and back) for that side, and they will probably look similar, bouncing all over the place. A good working cat will produce a straight line or at least a relatively smooth curve. What probably happened is your rear O2 sensor was also getting lazy and didn't pick up the rapidly switching mixture, which basically fooled the computer into thinking the cat was working fine. When you changed the sensor, it was able to pick up the failed cat. In a state with OBD2 emissions, I've learned to never replace a rear O2 sensor unless it sets a code that it's bad (rare, in my experience) because it can help mask a failed cat and hold off more expensive repairs.
 
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