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2013 Chevrolet Suburban 5.3L P0068 Fault: Loss of Engine Power After AFM Lifter Replacement

Model: 2013 Suburban Fault Code: P0068 Posted: 2016-11-28 23:44

I recently completed replacing the AFM lifters in my 2013 Chevrolet Suburban 5.3L V8 engine. After reassembly on Sunday, the vehicle ran smoothly for several days and sounded significantly better. However, late this afternoon, I lost all engine power while driving about one mile from home. The vehicle now fails to start and displays a persistent fault code: P0068. The issue is particularly puzzling because the truck was running well immediately after the repair. It now stalls completely when attempting to start, stumbles during cranking, and shows no signs of ignition or engine movement. I have a Bully Dog OBD2 scanner installed, which has allowed me to detect the P0068 code—though it does not currently provide live sensor data. I'm seeking expert input on possible causes for this sudden failure. The PCM is reporting conflicting inputs from the MAF (Mass Airflow), MAP (Manifold Absolute Pressure), and TP (Throttle Position) sensors, which are inconsistent with normal engine operation (e.g., high airflow at idle, high vacuum readings). I have no aftermarket air filters, performance chips, or modifications installed. I've already verified that all sensor connectors are securely plugged in. Fuel pressure is within normal range, and spark is present across all cylinders. The vehicle still attempts to crank for a few seconds after the ignition key is turned off—a sign of residual electrical activity—but no engine starts. Could this be related to a failed sensor, wiring issue, or a more serious mechanical failure such as fuel/oil contamination in the intake manifold? I've found a large pool of fuel and oil inside the intake manifold—what could cause this sudden accumulation?

Related fault codes

P0068

Comments (6)

Anonymous 2016-11-29 08:18

Lost all power? That suggests an electrical issue or possibly engine-specific loss. Could you clarify if it's total vehicle power loss or just engine power? For engine-related issues, first check: are all fault codes visible and is live data accessible via your scanner? P0068 indicates the Powertrain Control Module (PCM) detects conflicting sensor inputs—specifically from MAF, MAP, and TP sensors. These readings don't align logically (e.g., high airflow at idle with high vacuum). The vehicle is stock—no air filters, chips, or modifications. This could point to a faulty sensor or wiring.

Anonymous 2016-11-29 15:01

Apologies—I meant 'loss of engine power,' not total vehicle power. I use a Bully Dog OBD2 scanner for diagnostics and have had it installed for years. It does show the P0068 code, though live data is currently unavailable. The truck ran perfectly after the AFM lifter replacement and sounded much better. The sudden loss of engine power is very unusual. I had to coast to a stop and when attempting to start, the engine stumbles and seems to try to ignite but fails to fire. Thanks for the quick response, kev2! Any insights would be greatly appreciated.

Anonymous 2016-11-29 15:16

NO—no K&N air filter installed. I’ll verify whether Bully Dog shows all codes from P0999 upward; I assumed it did but need to confirm. Please check that the MAF, MAP, and TP sensors are properly connected. After clearing the code, does P0068 reappear? A SWAG (suggested workaround) is to test fuel pressure using a dedicated gauge—this could rule out fuel delivery issues.

Anonymous 2016-11-29 15:38

Correct—no K&N filter. I’ll research the Bully Dog’s capabilities to confirm whether it reads all P0999+ codes, as I assumed it did but want to be certain. I’ve already rechecked all sensor connections and they appear secure. The code reappears when attempting to start. I’ll perform another diagnostic run—though it's currently cold outside, so I won’t attempt it in freezing conditions. I’ll also test fuel pressure to ensure the system isn't experiencing a delivery issue. Thanks for your help!

Anonymous 2016-11-29 19:25

I’ve rechecked all sensor connectors and they appear properly connected. I will now test each sensor individually to identify any potential failures. The P0068 code returns every time I attempt to start the engine. Spark is confirmed across all cylinders, fuel pressure is normal. The vehicle still cranks for a few seconds after turning off the ignition key—a sign of residual power but no actual engine start.

Anonymous 2016-11-29 23:30

I discovered a significant pool of fuel and oil inside the intake manifold. What could be causing this sudden contamination? Is it possible that a failed lifter or internal valve issue led to oil entering the combustion chamber and mixing with fuel, resulting in both the P0068 code and the physical buildup?