mtuggle86

iTrader: (7)

ok my car has no check engine light on and no stored fault codes but at the not ran codes scc menu on my predator these codes show up are they pending? my car runs very cold 150-160 degrees im changing the thermastat on monday how many of these codes could be caused by that im thinking the 02 codes could be cause buy the combustion temps being cold and not helping the 02 get to operating temps fast enough even though there heated any other ideas or am I just wrong?

p0125
p0135
p0141
p0155
p0161
p0420
p0440
p0442
p0446
p0500
p0704
p1441
p1539
p1546

Mike454SS

iTrader: (4)

Code 125 is definitely from the engine running too cold, and I also kinda agree with you about 135, 141, 155 and 161.

You've got a bunch of EVAP and VSS related codes too...does your speedometer work?

I think when you get the thermostat fixed some of your codes will go away (get the engine up to temp)...but you also need to figure out whats up with the VSS and EVAP stuff as thats most likely not related to the temp. Check the gas cap for starters...but I don't think thats going to be the EVAP problem...but the VSS issue could be the EVAP problem too...EVAP won't work right if the car doesn't know when it's moving.

99bowtieZ

It's a start...

mtuggle86

iTrader: (7)

speedo works fine that one I can't think of y that one showed up maybe its on its way out? But as for the evap will it effect power or drivabilty? if not Im in michigan and dont have emissions tests so I dont care about the evap system

99bowtieZ

Quote
In new Chevrolet vehicles, specifically on those equipped with an anti-lock braking system, two speed sensors are usually installed. The first is the engine speed sensor. This speed sensor is often mounted on the vehicle's crankshaft and is actually where the speedometer gets its data. The other type of speed sensor used in modern vehicles is the wheel speed sensor. This speed sensor, on the other hand, picks up impulses from the wheels and sends the data to the anti-lock braking system (ABS) ECU. This data is then used by the system to anticipate a condition when the wheels would lock-up.

Now, what happens if these two types of speed sensors fail or malfunctions? Nothing much, probably, in the case of the engine speed sensor. The only complication it will make is that the engine management ECU won't be able to measure the engine speed and thus you won't be able to determine how fast your Chevy is moving through the speedometer. But if the wheel speed sensor is the one that fails, then you are in serious trouble. If this happens, your ABS brakes would become totally useless as there is nothing that will tell the system that your Chevy's brake is already locking up.

mtuggle86

iTrader: (7)

its hasnt failed yet it hasnt flipped the CE light on yet maybe it got some water up there?

99bowtieZ

Unplug your battery, then plug it back up and start the car then read the codes again (see if it's the same). Did you do anything that caused it to show up any of those codes?

Mike454SS

iTrader: (4)

You can ignore the thing about the ABS...VSS is the sensor on the back of the transmission and it's not anything to do with your ABS. Maybe it was an intermittent code...I'd fix the thermostat so that the car runs at normal temp, then clear all the codes and see what comes back, then continue troubleshooting from there.

Greg Pippin

iTrader: (3)

if its running that cold without a tune it will set some off the wall codes. your cars computer is stuck in "closed loop". you need to replace the t-stat and get all your emissions stuff tuned out of the computer.

mtuggle86

iTrader: (7)

I dont think its stuck in open loop mode the thermastat will go on monday the codes where not ran codes so I think if it was stuck in open loop it would have thrown a ce light Ill see on monday what it ends up doing

Greg Pippin

iTrader: (3)

if the engine want heat past a certain temp, the computer want/cant run certain test.

Mike454SS

iTrader: (4)

You don't have a good understanding of the PCM.

Closed loop is PROPER operation, but it requires the engine to be up to operating temperature. From a control systems standpoint, closed loop means that the computer is monitoring input and output, and using the output to adjust the input.

Open loop is what you get when you first start the car, it runs, but it ignores the O2 sensors (the sensors that monitor output) until everything is up to temperature. They don't react properly until they're warm hence the delay. Once everything is up to temp and a time threshold has gone by, the computer then listens to what the O2 sensors are saying, and uses them to adjust the raw input from the MAF, coolant temp sensor, intake air temp sensor, MAP sensor and so on to fine tune the air fuel ratio.

By setting the codes the OP's car is setting, it is also saying "I'm staying in open loop".

For 99% of the cars on this forum, closed loop is a good thing...takes a very very ridiculous engine setup to warrant going to open loop.

mtuggle86

iTrader: (7)

If it was stuck in open loop wouldn't it trip the CE light? The codes come up but there not stored codes there not ran scc codes please explain way they are. Are they pending codes?

Greg Pippin

iTrader: (3)

im sorry for saying "closed loop" instead of "open loop", i got my words mixed up.
I was just trying to help out....

Yall have a nice day.

good luck on your atd diag...