KySilverado

iTrader: (7)

Guys, Truck has been down for 3 weeks. Waiting on new tranny and getting it in. Finally buttoned it up this morning and went to start it for first time and it won't.

Throwing these codes picked up with HPT. I also turned off VAT's with HPT and loaded that program thinking it might be that and a no go.

P0335 - CKP Sensor A Circuit Performance
p0335 Crankshaft Position Sensor A Circuit Malfunction (more specific)
U1026 - Loss of ATC Class 2 Communication
u1026 Transfer Case Shift Control Module (more specific)

Wondering if they are related.... a shared wiring harness maybe damaged? Doesn't look like it since they run down different harnesses best I can tell. I know I had them all disconnected when I pulled the tranny. So I didn't stretch any. Only thing I don't know is if they could have/can be damaged when the engine tilts when you remove the cross member and drop the end of tranny down to get up to the top bolts and such. This is the third time I've had the tranny out and did it the same way, so I don't think this could have damaged any wiring. I've checked all the connections to the transfer case again. They are in and tight.

I am thinking the Crank position sensor is the no start issue?

Can't remember does the Check engine SES light come on and stay on with the ignition on before starting? Mine is. The system check on HPT reports complete when I connect.

Anybody have any ideas?

TIA

gonzo 6.2

iTrader: (8)

Fuse. and yes,I believe the light will stay on until it starts.

KySilverado

iTrader: (7)

Thanks for the input gonzo. First thing I did was unhook the battery and last thing was hook it back up. I looked at all the fuses that might have something to do with it. Gonna get on my GM tech site and check the specific circuit out.... no fuses blown that I see so far.

Thinking back I got fairly aggravated at the darn starter wanting to fall down and was tucking it back up in there fairly hard. Appears also that the crank sensor is very close to the area I was using to tighten up the TC, might have gotten into it when I was torquing down on the bolts. I'll pull the starter and have a look see ohm it out.

Will the P0355 malfunctioning CPS cause a no start.... I think it will.

gonzo 6.2

iTrader: (8)

I felt kind of dumb bring up "fuse" i know you'v been around the horn enough to check them at the slightest doubt.So its cranking but not firing right?Your gut is saying crank sensor because its not firing? right?

KySilverado

iTrader: (7)

Well my gut and the code its throwing. Yes it is cranking fine. I've actually not checked to see if it is firing the plugs. I'm betting it isn't.

gonzo 6.2

iTrader: (8)

And you can hear the fuel pump?

KySilverado

iTrader: (7)

Yes, I can hear the fuel pump and have fuel pressure on the gauge.

DrX

iTrader: (7)

DTC P0335

Circuit Description

The crankshaft position (CKP) sensor signal indicates the crankshaft speed and position. The CKP sensor circuits are connected directly to the powertrain control module (PCM) and consists of the following circuits:

• The 12-volt reference circuit
• The low reference circuit
• The CKP sensor signal circuit

If the PCM detects there is no signal from the CKP sensor for 8 seconds, DTC P0335 sets.

Conditions for Running the DTC

• DTCs P0101, P0102 , P0103, P0341, P0342, or P0343 are not set.
• The camshaft position (CMP) sensor signal is incrementing.
• The mass air flow (MAF) is more than 3 g/s.
• The ignition switch is in the Crank position.

<Conditions for Setting the DTC

The PCM detects there is no signal from the CKP sensor for 8 seconds.

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
• Clear the MIL and the DTC with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if the fault is present.
2. This step simulates a CKP sensor signal to the PCM. If the PCM receives the signal, the fuel pump will operate for about two seconds.

(System wouldn't accept my post unless I cut it short. I omitted the test sequence.)

DrX

iTrader: (7)

I was pretty rough on that too. Much easier after I remembered to remove the oil dipstick tube.

KySilverado

iTrader: (7)

Looks like you have access to GM's service data also. I have this and other information printed out, ready for my next jaunt under the truck. Thanks for the post!

Really a bad day... will be a while before I get back at it. The truck had me bummed out... right after posting this thread I received a call. My father passed away this morning.