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Need Help got DTC's!!!!!

Robby Avery

Robby Avery

New member
Need some help on DTC's! My girlfriends car has me pulling my hair out trying to figure out where to start to get it running right again before I do any performance mods to it. I have EFI Live so I pulled the DTC's out and wrote them down. They are P0300, P0420, P0742, P1811, all are pcm related. I'm pretty sure the P0300 is a misfire code so that would be coil pack related right? The rest of the codes I have no clue about as my computer starting dying before I could scan the codes with the EFI Live scan tool. I'm new to the GP world so bare with me but I'm pretty good with GM's since I own to duramax's. Thanks in advance
 


if you have a fax number i can try to fax over the alldata info for those dtc pretty sure the p0300 is misfire related to the others. p0742 is a transmission fluid pressure switch. and p1811 is related to p0742. p1811 is related to the misfire. has to do with the 02snsr reading
 
0300=random misfire code.
0420=Rear cat code. Tranny referance Issues:http://www.tripleedgeperformance.com/Harsh_shifts__P0742.html
Po742=When this trouble code is set the pcm will command max TCC and lock adaptive shifting. This code can be broken down into three potential problem areas as found to be common in the field.
1. This problem can be a mechanical problem. Possible causes of this could be a bad or stuck TCC switch that signals the pcm of current TCC operation. Another cause though not common is a stuck TCC switch or apply valve. If it is physically stuck in the wrong position it can cause the TCC to be stuck on all the time and even kill the engine when the vehicle is put into gear.
2. This problem can be found to be an electrical problem. If the wire from the TCC pressure switch to the pcm is grounded anywhere in the path it can throw this code. This could be a wire shorted inside the trans on the internal wiring harness or the actual engine wiring harness. If the wire is grounded the pcm thinks that TCC is on when it shouldnt be and will throw the code.
3. This problem can be a hydraulic problem. This is the most common cause of this code that I have found and stems back to a clogged TCC solenoid, not because it failed. Excessive debris in the transmission or a failing torque converter lockup clutch can cause the solenoid to have debris stuck inside and this causes a restriction in fluid flow through the solenoid. If the solenoid can not bleed off the pressure the TCC can be stuck on. If the wrong TCC solenoid is installed during an overhaul this problem can also arise as a late 4L60E solenoid is identical but does not operate the same and acts like a clogged solenoid. As mentioned in problem #1 a stuck TCC apply valve is a physical problem but causes a hydraulic problem because the fluid pressure will not properly bleed off because the valve is stuck in the wrong position instead of being able to move freely in the bore of the valve body.


P1811 is a max adapt shift code.
This code will set when the pcm/tcm detects excessively long shift times. For every shift the pcm/tcm watches how long the shift takes to complete in milliseconds. If the shift times are over roughly the .06 second timeframe and the pcm/tcm tries to compensate for this by raising line pressure and still does not see acceptable shift times after a few shift cycle it will trigger code P1811. When this happens it puts the transmission in a max line pressure condition to help protect the transmission against excessive slippage and burnt clutches. While this condition is present you will feel harsh shifts, some vehicles more agressive than others, and you will also hear a whine noise similar to what a power steering pump that is low on fluid will sound like. You can shut the engine off for a brief moment and restart the vehicle and it will feel normal again until a few shift cycles of excessive shift times and the cycle will repeat itself. This typically only happens after you have driven for a short while and the transmission and its fluid warms up.

Some common causes to this problem are-

-Poor working PCS (Pressure Control Solenoid), also called EPC or Force Motor
-Excessive clutch clearances
-Poor functioning accumulator system
-Worn internal seals and sealing rings
-Excessive valve body wear
-Dirty MAF sensor resulting in lower commanded line pressure
 
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Thanks guys I'll start with some of the solutions ya'll have giving me. She has the wiring recall that GM mailed out I'll take it to the dealer first to have that done before I start digging in to see what all needs to be fixed. So with all the codes relating to the other could there be a faulty coil pack or should I start by checking the MAF first then cleaning it and then go for the big stuff? Give me some steps to follow to track the problem(s) down so I can get this thing fixed and running right again. Also Would the Trans codes be related to the shutter she feels in the lower gears or is the trans fixing to take a poop on me? Again thanks in advance
 
I was wondering after posting this thread could a clogged cat be a culprit to some of the codes I'm seeing? I know its not related to the trans codes thought
 


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