Hello Group,

Long-time lurker here; 2001 F150 S-Crew 4.6, 4x4, 255k miles -- have been chasing a P0171, P1132 and a P0301.

The P0301 misfire, I "believe" may be caused by a short or open ground in the Bank 1 injector harness. Reason I say this is because when monitoring my O2 sensor readings on the scanner tool, the voltage is flatlined at 0v, however when moving/jiggling the Bank 1 Injector harness, the 02 readings come to life briefly.

Now, if anyone knows what the resistance I should be looking for when measuring from the terminal at the Injector connector for the send wire to the cluster of wires at the 42-pin housing, it would be greatly appreciated.
I won't go into all of the previous troubleshooting I have completed for the codes as I am past that; at this point it is either electrical short or a base timing issue which I will address later once the electrical suspicion is confirmed moot.

 

You ask a really good question that needs some surprising explanation.
First, the 30x codes are generated when any cylinder's rotation time is too slow>>> as measured by the Crank's sensor RPM report to the PCM.
The slower rotation time is due to cylinder mechanics, lack of fuel, head gasket leakage, coil secondary or leaking boot failures, or any fault that reduces cylinder pressures [after ignition occurs].
Second, 35x codes are a monitor of the coil >>electrical << circuit continuity, crosses and groundouts as measured by the PCM.
This means wire harness, connectors, coil (primary failures), PCM Coil Driver failure.
.
You can see the two totally different misfire failures that are detectable by different monitors/codes for every cylinder every time in the fire order.
Fuel injectors have there own separate failure codes.
All three failure type codes will affect Ox Sensor readings in one of only two ways they can only respond to exhaust conditions..
A. Lack of Oxygen levels indication an over Rich fault condition.
B. Excess Oxygen levels indication an over Lean fault.
.
Returning to your 30x code and matching it to the way it was generated leads to cylinder slow rotation time looked at over a number of rotation time intervals for Logic to make a decision is is to be a 30x type failure.
Therefore, thinking it would be a harness failure involving a open circuit would not be the first choice to consider.
There is a thin line between coil primary and secondary faults, considering the primary is monitored for electrical current, the secondary is not and only by rotation time detected by the Crank sensor..
You can see the differences in these parameters with virtually no crossover and designed to be very accurate.
.
Be sure the injector plugup is seated and solid. This will instantly reflect cylinder pressure on an intermittent basis before an open injector code would develop. It depends a lot on absolute time durations. The code 30x pretty well defines the type of failure.
.
You ask about resistance measurements;
The Coil Drivers are solid state switches in the PCM that are commanded to close a ground out to the coils per the cylinder fire order and Current measured.
A means has been provided to test continuity from the coil connector looking back to the coil driver.
A 10,000 +/- resistance exists from the driver lead to ground that can be tested for to prove the individual cylinder drivers circuit continuity.
This resistance 'value' is too high to cause shunting of the injector that has a very low resistance .
Measuring it should not see an open, much higher value, much lower, a cross to another lead, or low value short to ground. This same check can be used to look at the Injector drivers..
.
To further check misfires using a Good Scanner, look into Mode 6 at test 53 where you can see the misfire counts for each cylinder as pass of fail with in program limits.
Bottom line is there's more to all this than meets the eye, you needed to know about.
Good luck.

 

Bluegrass, thank you for replying with great detail and thought. So, with that, am I chasing a rabbit when it comes to the wiring harness? If I may add, the connectors are loose also; perhaps the vibrating engine is jarring the contacts?
should I dive in to just replace the timing components and, most likely expected broken chain guide?

 

I don't know the rest of your concerns.
I recommend never to launch into just parts replacements until proven the need.
It waists money and time plus dis-satisfaction if it does not clear any issues, then your back to square 0ne.
Good luck.

 

None of those codes are pointing to a timing issue.

 

I agree, but the cylinder 1 misfire "might" have been inadvertently caused by a timing issue... at least that's what the Stealership told me, and they can confirm this for the low, one time cost of $459, and if confirmed, make the repair for a mere $2235!
UPDATE: reading Bluegrass's detailed answer over and over and thinking about it logically, I decided to swap the bank of injectors, 1 to 2 and 2 to 1, just to see if the problem followed, plus replaced the #2 injector, #2 and #3 injector connectors as the wires in the loom were a bit crimped, pinched and flat.
Well, all the codes now are gone after cycling! No misfires in Mode 6, and just a slight O2 variation, not enough to be of an issue though.
So thank you to this forum and experienced members for the input!

 

Good for you.
It would appear a connector/connection seating was intermittent on one injector.
Good luck, put de check in de mail.
Ya know what they say,,,$10 for the part and $1000 for the advice.
Take care.