Engine/Transmission (1998.5 - 2002) VP44 Injection Pump/Connector Wiring...

[2-ND TIME]

APPS

John- K5AWO Thanks If two different restats had different resistances would that change the voltages that the transistors, op- amps would see and change their signals and opperate differently? The new APPS that I measured were in the dollarships for most won't return electricial parts. With high contact resistance on pins 1,6and 1,2 wouldn't this change the how the ECM sees the off- idle signal and change the fueling accordingly ???

 

[justinp20012500]

Originally posted by MCummings

I just took that adaptor apart earlier today trying to chase down a P1689 (No communication between inj. pump and ECM), and found the same thing, except my wires werent creased. There was a green wire (Adjacent from the empty slot) that had it's actual wires exposed.



I'm still hunting down my no Comm. problem though. .



Merrick

I threw that code about 2 seconds after change my fueling box ground wire from the Black/brown line wire in the harness to the ground on the battery. When I moved it back to the harness ground and soldered it instead of the scotch lock it has went away. My buddy has expierenced the same results.

 

[Gary - K7GLD]

"

I threw that code about 2 seconds after change my fueling box ground wire from the Black/brown line wire in the harness to the ground on the battery. When I moved it back to the harness ground and soldered it instead of the scotch lock it has went away. My buddy has expierenced the same results. "



HMMMmm - that suggests a significant difference in ground potential between what the wiring harnees "sees" as ground, and what is actually present at the battery - I would take a hard look at the harness grounding point to make certain it is clean and secure - otherwise, other random problems are likely to crop up...

 

[John - K5AWO]

<<<<moved it back to the harness ground and soldered it instead of the scotch lock it has went away>>>>



I agree with Gary. There are some potential bad ground problems lurking in your truck. You might want to consider running some #12 or #10 soft, stranded wire from the battery to the different ground points in the harness. Be sure all the connections are bonded good. Solder is best if done right. A poor solder job is worse than a butt splice and those Stake-On pliar crimp tabs are the worst of all. They break wires when punched, vibration sets in at the joint and it all breaks sooner or later.

 

[John - K5AWO]

Re: APPS

Originally posted by 2-ND TIME

John- K5AWO Thanks If two different restats had different resistances would that change the voltages that the transistors, op- amps would see and change their signals and opperate differently? The new APPS that I measured were in the dollarships for most won't return electricial parts. With high contact resistance on pins 1,6and 1,2 wouldn't this change the how the ECM sees the off- idle signal and change the fueling accordingly ???

IF all of the APPS modules you are looking at and have measured are the same part number..... yes, I agree with what you are saying. But a real accurate answer needs to know exactly what each resistance is doing in the circuit.



A typical op-amp with a bias set point midway between two 5k resistors will see 1/2 Vcc. Likewise, if those two resistors were 500k, the bias set point will still be 1/2 Vcc. Since op-amps are very high impedance input devices, they draw a very neglible amount of current and the actual resistance value won't mean much in a voltage divider circuit.



However, if those resistances are being used to control the timing of a clock circuit, a significant departure from the design value will render the controlled device inoperable. The timing would be out of limits.



Unfortunately, I personally have no experience with the internal workings of the APPS unit. I only have my past technical experience to draw conclusions based upon the information provided. Many a savage sage has concluded and heard the adage: "Garbage In equals Garbage Out".



From the info I have picked up on from the TDR threads, I am inclined to believe that the APPS module is controlling a variable pulse width timing signal. The ratio of the "ON" time relative to the "OFF" time is what the computer is looking for. More ON time equals more fuel to the injectors. (Beware of assumptions - another old adage).



None of this has given you a definite answer. Access to the original technical documents used to design the system would be very beneficial. In my world of working with radios, telephone systems and computers, we attend factory schools that go in depth explaining the theory of the circuitry involved. Without that inside knowledge, it is a very rough row to hoe trying to learn all the actual facts of how a circuit works.



Confused as I am?