You’re driving along, minding your own business thinking about how great life is because of your 5.9 cummins and then it happens:
- Your dash binger goes off 10 times
- Your heater grid light comes on and stays on
- You are in limp mode with about half of your normal engine power
Of course you are a savvy Cummins guy, so you immediately check for Diagnostic Trouble Codes and see either P1222 and/or P1223 which leaves a lot of guys scratching their heads wondering “What does that mean?”
If you have just installed a Smarty Tuner such as an s06, Smarty Touch or MM3 make sure you read to the end!
P1222 Defined: “LEAK DETECTION DURING MOTORING”
TSB 18-006-12: “When engine is motoring (i.e. Engine is running, but requires no fuel injection) the only
required fuel delivery to the rail is due to natural leakage in the system. The natural
leakage depends directly on the rail pressure. A definite amount of fuel is required to
overcome the natural leakage, for different fuel pressures. The Engine Control Module
(ECM) sets Leakage Detected, when the fuel flow exceeds an expected value. When a
leak is detected in the system, a counter is initiated. When the counter reaches a
predetermined value a fault is set and engine derate is enabled. When the leak is not
detected the counter counts down, and once the counter becomes zero the engine is set
back to normal running conditions.”
P1223 Defined: “LEAK DETECTION BASED ON QUANTITY
TSB 18-006-12: “There is a required amount of fuel required by the fuel system to keep the system stable.
The amount of fuel required depends on fuel pressure, injection quantity, engine speed,
and coolant temperature. The Engine Control Module (ECM) sets Leakage Detected, when
the fuel flow exceeds an expected value. When a leak is detected in the system, a counter
is initiated. When the counter reaches a predetermined value a fault is set and engine
derate is enabled. When the leak is not detected the counter counts down, and once the
counter becomes zero the engine is set back to normal running conditions.”
These tests were NOT INCLUDED in the original factory software!
These tests were added as a “software update” some time after these trucks had been on the road. This is why people get this code “out of nowhere” after returning from a trip to the dealer or installing a Smarty Tuner. In both cases, your truck has been brought up to the latest software revision and now includes these tests.
For the most part, it has been found that these tests do identify a real problem with your truck. This issue may have gone un-noticed simply because your truck wasn’t checking for these problems originally. Now that you have had a dealer flash to your ECM or used a Smarty Tuner (which always uses the latest dealer software), your truck is now checking for these problems and it turns out a lot of trucks have these issues.
Great, how do I fix it?
I am attaching the Technical Service Bulletin (TSB) below which has the entire dealer diagnostic procedure. However, the most common cause of this code is one or more failing injectors. Secondary causes can be a bad Fuel Control Actuator, Pressure Relief Valve, Cascade Overflow Valve or leaky fuel tubes.
One thing you can try that only costs time is to retorque your fuel delivery tubes to 45 ft/lbs and see if that clears up your codes.