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I am having issues with the car (2007 G35 Sedan), last month these two codes started popping up:
Code P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
Code P0128 (Pending Fault) - Coolant Temperature Below Thermostat Regulating Temperature
Most of the time it's P0430 alone, but sometimes they pop up together.
I was having misfires on Cylinder 4 (Bank 2), changed the spark plug on that cylinder, no more misfires, but the two codes still come up.
I went under the car and saw a pinhole on bank 2 (before the bank 2 downstream oxygen sensor). Not sure if the pinhole goes all the way through. However, the downstream bank 2 oxygen sensor voltage has not been holding steady and has been zigzagging similar to the bank 2 upstream oxygen sensor.
Do you all think that this is the cause of the P0430 code and how does the P0128 (pending) code tie into this? Does the P0128 (pending fault) code mean my coolant thermostat is bad or stuck open?
From a cold start letting the vehicle idle, use a timer and measure two things:
-How long does it take for the needle to reach the center of the COOL mark (first hash mark on the gauge).
-How long does it take for the needle to reach operating temperature which should be just slightly under the middle value of the gauge.
Do not DRIVE the vehicle to warm it up, don't rev the engine, just start the car and let it idle up to temp while you use a stopwatch to measure those two things. Post the results.
Next, with the engine at operating temperature how hot is the thermostat housing? Use an infrared temp scanner to check, if you don't have one then skip this for now.
I suspect you have a thermostat stuck open and it will take a significantly long time to warm up.
I also suspect you need to replace the other 5 spark plugs, if one failed due to wear then the other 5 are almost fried as well.
From a cold start letting the vehicle idle, use a timer and measure two things:
-How long does it take for the needle to reach the center of the COOL mark (first hash mark on the gauge).
-How long does it take for the needle to reach operating temperature which should be just slightly under the middle value of the gauge.
Do not DRIVE the vehicle to warm it up, don't rev the engine, just start the car and let it idle up to temp while you use a stopwatch to measure those two things. Post the results.
Next, with the engine at operating temperature how hot is the thermostat housing? Use an infrared temp scanner to check, if you don't have one then skip this for now.
I suspect you have a thermostat stuck open and it will take a significantly long time to warm up.
I also suspect you need to replace the other 5 spark plugs, if one failed due to wear then the other 5 are almost fried as well.
Prior to Start: 68 °F (Coolant Temperature: Torque App)
2 Minutes and 22 Seconds 123.8°F (First Dash on temperature gauge, Middle of C)
8 Minutes and 30 seconds 159.8°F (At center)
10 minutes 167°F
Last edited by michael j; Jun 13, 2020 at 06:34 PM.
From a cold start letting the vehicle idle, use a timer and measure two things:
-How long does it take for the needle to reach the center of the COOL mark (first hash mark on the gauge).
-How long does it take for the needle to reach operating temperature which should be just slightly under the middle value of the gauge.
Do not DRIVE the vehicle to warm it up, don't rev the engine, just start the car and let it idle up to temp while you use a stopwatch to measure those two things. Post the results.
Next, with the engine at operating temperature how hot is the thermostat housing? Use an infrared temp scanner to check, if you don't have one then skip this for now.
I suspect you have a thermostat stuck open and it will take a significantly long time to warm up.
I also suspect you need to replace the other 5 spark plugs, if one failed due to wear then the other 5 are almost fried as well.
You are right. Replaced my thermostat. Car was running really cool in the 160's and 170's while driving and would take forever to warm up. Car heats up to 180's/190's quickly now. The Catalyst Monitor Bank 2 are also now good on Torque App, it appears that bank 2 didn't like the cooler temperatures and associated richer fuel mixture. It looks like replacing the thermostat resolved both of the codes. Thanks for your help. Will keep you guys updated if anything pops up again.
Last edited by michael j; Jun 13, 2020 at 06:38 PM.
