I have the 1996 silverado 350. I have a Haynes repair manual and have
done a few test. The problem was bucking but sometimes the truck would
run just fine. I had the ignition module checked at autozone. it
tested bad they said and i got a new one. However, the code came back
the next day.

I did all the checks on the coil with a volt meter. It checked good.
The ignition module, coil and crank position sensor all have 11.5-12
volts supply voltage. The ground wire in the harness has continuity to
battery ground.

Checking the ignition control module harness white wire with a
voltmeter on AC mode should yield "approximately"1.0 to 4.0 volts with
the engine cranking. It yielded 6.0 volts in my test. it says to check
the crankshaft sensor if the voltage is out of range. Backprobing this
sensor with a voltmeter on AC should result in "approximately" 5.0
volts. My test resulted in 3.9-4.0. The manual then says: "If a CKP
sensor signal is not present, replace the crankshaft position sensor."

Well, my voltage was out of the 'approximate" range, but a signal was
present.

It goes on to say if the ignition control module test and the
crankshaft position sensor tests are ok, to have the PCM checked at a
dealer.

This is my daily driver but the truck has 342,000 miles so I dont want
to spend to much at a dealer.

Where should I go from here? Replace the crankshaft position sensor? I
have read something about there being a "relearn" process that has to
be done by a dealer sometimes when replace ing this sensor? Could I
still drive it?

I really appreciate your help!

On Thu, 24 Nov 2011 20:52:05 -0800 (PST), stryped
wrote:

I have the 1996 silverado 350. I have a Haynes repair manual and have
done a few test. The problem was bucking but sometimes the truck would
run just fine. I had the ignition module checked at autozone. it
tested bad they said and i got a new one. However, the code came back
the next day.

I did all the checks on the coil with a volt meter. It checked good.
The ignition module, coil and crank position sensor all have 11.5-12
volts supply voltage. The ground wire in the harness has continuity to
battery ground.

Checking the ignition control module harness white wire with a
voltmeter on AC mode should yield "approximately"1.0 to 4.0 volts with
the engine cranking. It yielded 6.0 volts in my test. it says to check
the crankshaft sensor if the voltage is out of range. Backprobing this
sensor with a voltmeter on AC should result in "approximately" 5.0
volts. My test resulted in 3.9-4.0. The manual then says: "If a CKP
sensor signal is not present, replace the crankshaft position sensor."

Well, my voltage was out of the 'approximate" range, but a signal was
present.

It goes on to say if the ignition control module test and the
crankshaft position sensor tests are ok, to have the PCM checked at a
dealer.

This is my daily driver but the truck has 342,000 miles so I dont want
to spend to much at a dealer.

Where should I go from here? Replace the crankshaft position sensor? I
have read something about there being a "relearn" process that has to
be done by a dealer sometimes when replace ing this sensor? Could I
still drive it?

I really appreciate your help!


Start with basics, how are ther spark plugs? Spark plug wires? A bad
plug or wire can cause a coil to arc internally, you will never pick
that up with an ohm meter, but the coil will produce a weak spark.

Clean the grounds anyway. Bad grounds to all kinds of weird things to
computer controls engines.

Is the bucking engine cold or warm? speed? raining out?

Remove 333 to reply.
Randy

Think basics. Water in the gas? In my case, the NYS has gone
to gasohol, so we've got 10% drygas in the fuel already.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"stryped" wrote in message
...
I have the 1996 silverado 350. I have a Haynes repair manual
and have
done a few test. The problem was bucking but sometimes the
truck would
run just fine. I had the ignition module checked at
autozone. it
tested bad they said and i got a new one. However, the code
came back
the next day.

I did all the checks on the coil with a volt meter. It
checked good.
The ignition module, coil and crank position sensor all have
11.5-12
volts supply voltage. The ground wire in the harness has
continuity to
battery ground.

Checking the ignition control module harness white wire with
a
voltmeter on AC mode should yield "approximately"1.0 to 4.0
volts with
the engine cranking. It yielded 6.0 volts in my test. it
says to check
the crankshaft sensor if the voltage is out of range.
Backprobing this
sensor with a voltmeter on AC should result in
"approximately" 5.0
volts. My test resulted in 3.9-4.0. The manual then says:
"If a CKP
sensor signal is not present, replace the crankshaft
position sensor."

Well, my voltage was out of the 'approximate" range, but a
signal was
present.

It goes on to say if the ignition control module test and
the
crankshaft position sensor tests are ok, to have the PCM
checked at a
dealer.

This is my daily driver but the truck has 342,000 miles so I
dont want
to spend to much at a dealer.

Where should I go from here? Replace the crankshaft position
sensor? I
have read something about there being a "relearn" process
that has to
be done by a dealer sometimes when replace ing this sensor?
Could I
still drive it?

I really appreciate your help!

On 11/24/2011 10:52 PM, stryped wrote:
I have the 1996 silverado 350. ...
... The problem was bucking but sometimes the truck would
run just fine. I had the ignition module checked at autozone. it
tested bad they said and i got a new one. However, the code came back
the next day.

What specific code?

....

Checking the ignition control module harness white wire with a
voltmeter on AC mode should yield "approximately"1.0 to 4.0 volts with
the engine cranking. It yielded 6.0 volts in my test. it says to check
the crankshaft sensor if the voltage is out of range. Backprobing this
sensor with a voltmeter on AC should result in "approximately" 5.0
volts. My test resulted in 3.9-4.0. The manual then says: "If a CKP
sensor signal is not present, replace the crankshaft position sensor."

Well, my voltage was out of the 'approximate" range, but a signal was
present.

It goes on to say if the ignition control module test and the
crankshaft position sensor tests are ok, to have the PCM checked at a
dealer.

This is my daily driver but the truck has 342,000 miles so I dont want
to spend to much at a dealer.

Where should I go from here? Replace the crankshaft position sensor? I
have read something about there being a "relearn" process that has to
be done by a dealer sometimes when replace ing this sensor? Could I
still drive it?

Have '98 and '99 -- the '98 had same problem. The PCM was the issue

The equivalent of the Windows BSOD test is to read the OBD code. W/ the
ignition key in the "II" position read the OBD. A code value of P06xx
where xx=one of the values 01 thru 10 is a critical failure of the PCM.
If you get one of those it's toast and nothing else will cause joy.

I've not done the testing specifically so can't comment on various
observed symptoms as compared to the nominal given. The intermittent
nature appears to be related to the PCM from my observation; the other
sensors basically go and are consistent instead of come-n-go.

--

On 11/25/2011 3:59 PM, dpb wrote:
....

Have '98 and '99 -- the '98 had same problem. The PCM was the issue
....

I should have said similar _symptoms_; possibly not the same underlying
problem.

--