2000 Chevy Suburban P0430 ODB Code

2000 K1500 5.3 Suburbanwith 105K miles

Friday evening:

AC stopped working; engine temperature gauge takes a long time to reach the normal position.

AC compressor is not engaging

Saturday Morning:

Checked the coolant level and condition, all normal

Replaced thermostat, no change in gauge behavior

Added 22oz of R-143a, compressor engages every 15 seconds for about 1-2 seconds air is still warm, low side pressure is about 25lbs. Added another 22oz AC now blowing cold, pressure about 40-45lbs

?Service Engine Soon? light is now on code P0430 ?


AC working normally

Temp gauge still not working properly

Monday Morning (8/24)

AC is warm, compressor engages every 15 seconds for about 1-2 seconds

AutoZone pulled ODB code, P0430

Are the AC and temp gauge failures just a coincidence?

Should I now replace the temp sending unit?

What’s my next step?

Any help would be greatly appreciated



I would measure the ACTUAL engine coolant temperature with a thermometer. The output from the coolant temp sender can also be tested. With a new thermostat the engine should warm to normal temperature quickly.

I’m not an AC expert but I think your AC system has a refrigerant leak. I would take this to an independent AC shop. I’m not a believer in do-it-yourself AC repair.

P0430 indicates a catalytic converter operating below threshold. This could be caused by an exhaust leak, a malfunctioning O2 sensor, or the a problem with the cat itself. Pray it’s one of the first two.

Going to the shop for AC diagnostics tomorrow morning.

While researching P0430 I came across P0420 which seems similar but affects the other bank (Bank 1), it lists as possible causes “The engine coolant temperature sensor is not working properly”.

Can P0430 be reported as a result of “The engine coolant temperature sensor is not working properly”?


You are still saying that the engine coolant temperature sensor isn’t operating properly. Why? Don’t you trust it? Why not? If you want to know for sure, you can test it; or, it can be tested by someone.
The catalyst is the action of the catalytic converter. The catalytic converter cleans up the exhaust gases. If the engine is running too rich, the catalytic converter can be overwhelmed, and a trouble code can be set, such as P0420, P0430, etc.
The engine, actually being cold, can cause it to be enriched (with fuel). If the engine coolant temperature is reported low (by the ect sensor), to the engine computer, correctly or incorrectly, the engine computer will order a rich fuel mixture.
Take care of the engine problems, and the catalytic converter may not need further troubleshooting.

I’m concerned about the sensor because the gauge seem to move more slowly then usual to a normal operating temp, 200-205degrees, never exceeding that. I can’t think of anything anything else that would cause this behavior except for a stuck open thermostat which I already changed. Any guidance would be appreciated.

Does the same coolant temp sensor feed the gauge and computer?

Will the P0430 code ever clear itself if the condition that got it there is eliminated?

The ects sends its signal to the engine computer (ECM). The repair manual will tell you if the dash temperature gauge gets its signal from the ECM, or another temperature sender.
Is the radiator fan running when the engine is cold, and the A/C off? It shouldn’t. That would delay engine temperature rise to normal temperature. A stuck radiator fan relay is a possibility, if it runs.

No the fan is not running when the engine is cold with the AC off. What is an ECTS?

ECTS = engine coolant temperature sensor.

Certain GM trucks (my '96 S-10, for one) have a single coolant temp sensor sending its data both to the computer and the dash gauge. To my knowledge, the larger trucks have separate units. You really need to take a look in a Haynes or Chilton’s repair manual and see what your setup is.

There’s a quick way to test the gauge’s operation (assuming it uses its own sending unit). With the engine running, unhook the gauge connector from the sending unit and ground it against the engine. The gauge should deflect all the way to the max reading; if it does not, there’s a problem with the gauge or the wiring to the gauge.

Your full size truck actually has a electric fan and not just the mechanical?

Yes it has an electric fan


Mechanic pulled the code and diagnostic information, no definitive cause. He reset the code hooked up the monitor and road tested the truck, all sensors reporting normal operation. The o2 sensors before and after the catalytic converter were operating normally. Code has been reset for a couple of days now and has not come back on, so we’ll monitor for now.


AC Update:

Found the source of the AC leak, the rear lines are leaking just before the rear wheels. Lines are visibly wet and dye is evident. I’m waiting for a quote on line replacement, I’m afraid it’s going to be big $'s.

Is bypassing the rear air an option? I know it’s not ideal but the cost to replace the lines might be substantial.

Any other options? Can the lines be repaired with a splice?


$563.99 for each A/C line plus 5 hours labor, about $1500.00!!! Talk about sticker shock.

I think I see some AC lines getting pinched off.

Please explain

You said you can live without the rear AC. The rear AC lines are leaking. The proposed repair is very expensive. You can close off the rear AC, and stop the lines from leaking, by pinching those lines closed. Then, you would enjoy front AC.

Would I pinch both lines, in and out?
Would simply pinching them off seal them properly?

Can AC lines be repaired? I’d rather keep the entire system operational but replacing the lines is cost prohibitive. Help!