On Tuesday, August 28, 2012 07:04:43 PM you wrote:
> I'm at my wits end, replaced PCM 3rd time, still no start, no codes,
Are these new PCMs, or junkyard / refurbs or what? Are they actually known to
be working? It seems unlikely that you'd have a dead one, and get two
identically dead replacements.
> all looks good except no fuel signal to injectors, if I spray
> starter fluid runs fine.
So the fuel pump is running, and you've got pressure at the injectors?
> actually when I prob the signal side of an
> injector with a test light the truck fires few times cause apparently the
> test light is helping it fire the injector since the PCM
> isn't...
Looking at the FSM, it looks like the injectors get power on a common bus, and
the PCM controls the ground side. So if you put a meter on the power side, is
there 12V present?
If I'm reading the schematics correctly, you've got 12V from the battery
coming through the "automatic shut down relay" in the power distribution
centre. From there, it goes through "joint connector no. 2" in the PDC. After
the connector, it goes to all of the fuel injectors.
On the other side of the injectors, each one gets a line back to the PCM.
Since you have _no_ injectors, I'm thinking the PCM isn't where you should be
looking, but on the other side of the injectors where all of that common
wiring is.
> New Cam sensor, new Crank
> sensor(Bi^$@# of a time getting old one out!), have 12v at injectors, and
> spark...
Hmm. So you're pretty sure that the power side is good, then. And if you
ground the injector (like with the test lamp), then it sprays? How about
testing it the other way around, if you can? Hook the test lamp to power,
unplug the PCM side of the injector, and see if the PCM is switching ground to
it. That should light the lamp.
Looking further at the PCM, there's a capacitor on the +12V side of things,
tied to ground. It's not clear to me what that's for, unless it's just
providing electrical smoothing. But if that were bad, I'd expect it to either
drag the +12V down so that nothing worked, or to go up in smoke.
> saw few mentions of security enabled PCM's
> causing similar issues when installed in a truck w/o security?
> but
> does that kill the 12v or just the pulses???
> how do I find out if
> thats my problem???
Are you referring to the "Sentry Key Imobilizer Module" (SKIM)? If so, that's
on the steering column (do you have one? or not?), and the FSM says:
When the ignition switch is turned to the On posi-
tion, the SKIM transmits an RF signal to the tran-
sponder in the ignition key. The SKIM then waits for
an RF signal response from the transponder. If the
response received identifies the key as valid, the
SKIM sends a valid key message to the PCM over
the PCI data bus. If the response received identifies
the key as invalid, or if no response is received from
the key transponder, the SKIM sends an invalid key
message to the PCM. The PCM will enable or disable
engine operation based upon the status of the SKIM
messages. It is important to note that the default
condition in the PCM is an invalid key; therefore, if
no message is received from the SKIM by the PCM,
the engine will be disabled and the vehicle immobi-
lized after two seconds of running.
So I'm going to guess here that this isn't your problem. It says that it
disables the engine, but it doesn't say how. But it says "after two seconds",
and you're not getting even that far.
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