Can a faulty crank position sensor cause the system to be too rich? P0172


Asked by Feb 15, 2017 at 11:30 PM about the 2002 Jeep Grand Cherokee Laredo 4WD

Question type: Maintenance & Repair

I have been getting this code very often in the last three days. I had fixed all obvious  elements that can cause the system too rich problem but I still get the CEL with the same code. By elimination, I rule out the following elements:

Oxygen sensors,  MAPS, IAT, CTS, Fuel Pressure regulator, Air cleaner, fuel pump, injectors and spark plugs.

At this time, my prime suspect is the CPS because there was some oli leak in the valve cover, which may have damaged the CPS. But can this CPS really be responsible for the system too rich?

6 Answers


No, I'd suspect the MAF (Mass Airflow) sensor. That's the one thing that's not on your list of things checked. If it's dirty or malfunctioning it can cause the system to go rich. It's especially suspect if you have one of those cold air intake systems where you oil the air filter element. The oil will contaminate the MAF. An unlikely cause can be an exhaust leak ahead of the upstream oxygen sensor. If fresh air is being pulled into the exhaust stream, past the upstream oxygen sensor, it can cause the system to go rich. It's a rare occurrence, but it can happen. HTH. -Jim

1 of 1 people found this helpful.

Jim- Thanks for your response. I think the 2002 Jeep Grand Cherokee Laredo 4.7 L has no MAF. Am I wrong? If I am wrong, can you give me a hint on where to look for it?

1 of 1 people found this helpful.

Hmmmmmmm, interesting. You are correct. You don't have one! Oops!! Sorry about that!! -Jim

1 of 1 people found this helpful.

Over the last two days, I have noted that the System too Rich errors come ON and then go OFF by themselves when I drive over a considerably long distance. What is the matter?


I still need help on this question please! One critical sensor that I have never changed is the crank position senors and probably the idle air control valve. All other sensors are brand new (some areaftermarket and some are OEM).


Got no help here, however I researched further and the first prime suspect at this time seems to be the carbon build up on the valves and on the cylinders, It is associated with cold start misfires, which happens very often with my vehicle. I will try to decarbonize my engine to see its effects, so stay tuned to get my results of my experiments cum trials

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