POO11 2007 CHEVY 4X4 6.0L DOD VARIABLE VALVE TIMING
CODE FROM HELL!
This vehicle was setting code POO11 (valve timing advanced too far/ Bank 1). The code is a B code, so no check engine light came on. Traction control light would come on when the code set, which was the only indication of the problem, and the information center would read Traction Control Disabled and Stability Control Disabled. Oddly, the make and model of this vehicle has software programmed into the PCM to put the 4L65E Transmission in high line pressure when code POO11 set (which makes no sense). The PCM was a new GM computer with the latest software. When a 4L65E makes a 1-2 shift at highline pressure, it is a very harsh shift; the other shifts feel almost normal. The reason the 1-2 shift is so harsh and the other shifts feel normal is because of the wide ratio between first and second on that particular Transmission. The 700R4 Transmissions had this same problem, but the line pressure was controlled by the TV cable only, not the EPC. I found it odd for the software to raise line pressure to the max, so we decided to go after this P0011 problem. We checked for service bulletins about this problem. The information said to change the engine oil first, which we had done numerous times.
The next thing on the list, was to check or replace the variable valve timing components. We removed the timing cover and installed new timing chain and gears, chain guides, variable valve actuator and valve. We also replaced the PWM magnetic device that moves the valve, and installed a new cam sensor and a new oil pump. We removed the engine oil pan and cleaned the pickup screen, which was very dirty due to debris from cheap filters. The vehicle ran without any problems for five hundred miles before the code came back. This time, I was driving the vehicle up a 7 percent grade (a hard pull) when the code set; no check engine light, just the traction control light came on and the message center info that I mentioned earlier. So, we decided to look at this problem as an oil pressure or oil temp problem. We removed the timing cover to gain access to the oil pump regulator spring and valve. We shimmed the oil pump regulator spring .095, and that raised the base oil pressure about 10 PSI cold. Unfortunately, that did nothing to solve this problem. I hooked up my Tech2 scan tool and monitored the oil temp and the variable valve timing PIDS (the computer commanded timing and the actual valve timing in degrees). I could see when the oil temp reached 250 degrees the computer was commanding 20 degrees of valve timing change, but the actual timing change was only eight degrees. The code info said the timing advance between actual and commanded must not be more than eight degrees for 20 seconds at steady throttle. If the throttle was moved at all during the 20 seconds, the timer would start over. That’s one reason it was so hard to pin down this code. After knowing that, I could make this problem come and go at will. So, I decided to fill the crank case with 20w-50 synthetic oil. I hooked up to a big-ass trailer and pulled some steep grades trying to get the oil temp high enough to have the right conditions for the traction control light to come on and the code to set (remember, this happens "behind the scenes," as there is no check engine light). With 20w-50 oil I could not make the valve timing fail; it was always 20 degrees commanded and 20 degrees actual at 250 degrees plus. I could not leave the 20w-50 in the crankcase because the lifters would rattle on cold startup. I dropped down to 10w-40 synthetic oil, and the lifters didn’t make any noise on cold start up. I hooked back up to the big-ass trailer and starting pulling long steep grades; when the oil temp reached 240 degrees, the actual valve timing could not match the commanded valve timing with the 10w-40. By the way, the number 2 cam bearing feeds oil pressure directly to the valve timing actuator. Too much clearance in the #2 cam bearing causes pressure loss before it even gets to the actuator. We decided to install an engine oil cooler in series with the factory radiator engine oil cooler. The next test drive was a lot of fun because I could not get the problem to reoccur no matter how long or hard, I pushed the vehicle. My next test is to go back to 5w-30 synthetic engine oil. I call this a fix, and some of you might say this pickup needs a new motor, but sometimes it’s just fun trying to get over that hump. The customer has switched to 5w-30 synthetic engine oil with no problems. O by the way the customer didn’t pay one dime to figure out why this vehicle acted the way it did.
The oil temp on this engine is just a guess by the PCM. The engine oil cooler kept the oil viscosity up at high temps.
Paul Townsend
Paul's Transmission & Repair, INC.
Baker City, OR
97814
Paul Townsend
