Crank Issue

[chief404]

I'm having an issue with getting the goblin to crank. Fuel pump primes, throttle body moves with throttle - dash and everything comes on as normally with key on. When the key is moved to start, the dash/lights flicker and doesn't turn over. Leaving the key in and jumping the crank relay starts the car. The dash and everything else still works. No additional codes outside the typical evap. I tried switching the crank relay with another in the fuse box but still having the same issue. The last time I had a similar problem, it was a loose connection at the starter. I checked all my grounds and connection points, everything seems fine. Goblin has been sitting for a while but I go out and let it warm up every now and then, just started running into this issue. Looking for troubleshooting advice, I saw some other posts related to lan communication but the dash/power steering seems to be working as expected.

edit: starting to trace wires...85 on the relay should be the ground to the transmission...right? I checked with my multimeter to see if I get a ground signal at 85 to the engine mount area where the grounds are and got nothing. So..I'm assuming something is up with that ground? I may need to pull the fuse box and look at the wiring again. I will be surprised if that is an issue since this seems to just happened all of a sudden. The first time I had ground issues, I ran a bunch of extra thick wire grounds - one of them being the ground at the engine frame mount.

 

[Rttoys]

Have you load tested the battery?

 

[Gtstorey]

You have to be careful looking at the relay PIN numbers. The 4 pin relay will usually work no matter which orientation they are plugged in so the trigger side and the load side work on diagonals, unlike the way they are pictured on the wiring diagrams.

 

[chief404]

It's a relatively new AGM battery and was sits on a charger. I'm going to try running a new ground under the relay and see if that resolves it

 

[chief404]

You have to be careful looking at the relay PIN numbers. The 4 pin relay will usually work no matter which orientation they are plugged in so the trigger side and the load side work on diagonals, unlike the way they are pictured on the wiring diagrams.

Yeah I did check some other posts and saw something similar already said. I will test the ground again but on the other side of the diagonal since I already did one.

Won't crank with key turn

All those grounds should have ended up at G-105 back of engine stud. I think some of you put your ground wires on a chassis bolt under or near the fuse box. Put in the relay, but leave it up just a little and connect a ground jumper wire to the ground lug on the relay. This will bypass the...

dfkitcar.com

Also going to try running a new ground to the relay and see if that solves the issue.

 

[chief404]

So I just tried to run a new ground to 85 since I couldn't get a ground reading on either side of the 85/86 pins. Even with a new ground, it wouldn't start. Hot wiring the relay load side still works to start the car. The only thing I can think of at this point is that the ground trigger pins on the relay board don't get a good connection at all. I'll try to pull the fuse box tomorrow and check contacts. Anyone have any other suggestions on what I can test to narrow down the problem?

 

[Ross]

Sounds like when I had a data issue on the GM high speed LAN, but I was getting "Power Steering" errors on the dash.
Have you pulled the OBDii codes?

 

[chief404]

Sounds like when I had a data issue on the GM high speed LAN, but I was getting "Power Steering" errors on the dash.
Have you pulled the OBDii codes?

Yeah, I didn't see any new codes. I have always had a few evap codes. I'm thinking it may be the ignition fuse, since that also gives 12+ trigger via the clutch switch.

 

[chief404]

Checked the fuses and didn't see any issues there. Didn't have time to check today, but will try and test each side of the relay again and see what I get.

 

[Traé]

So I just tried to run a new ground to 85 since I couldn't get a ground reading on either side of the 85/86 pins. Even with a new ground, it wouldn't start. Hot wiring the relay load side still works to start the car. The only thing I can think of at this point is that the ground trigger pins on the relay board don't get a good connection at all. I'll try to pull the fuse box tomorrow and check contacts. Anyone have any other suggestions on what I can test to narrow down the problem?

I had a problem with the contacts on my fuse box being spread. I don't think it is very easy to get the fuse box apart to see these board. I ended up pulling the crank relay and slightly twisting the prongs to make sure they had good contact once plugged in. Worked like a charm!

 

[Gtstorey]

Are you getting 12v at one of the relay pins all of the time?

 

[ncgoblin]

I have a similar issue but with some additional complications. When driving recently I noticed a loss of power steering and fluctuation in gas/rpm gauges. Prior to this I also noticed sometimes the engine would start first turn others not for a while I figured this may have been linked to the switch. Now the engine will not crank at all. @Ross mentioned the High Speed LAN wires what was done to diagnose this?

Tonight I swapped the crank relay, removed crank signal wire from starter and when I turn the key no voltage. Pulled the clutch/brake switch from mount so I could test easier. Also jumpered A9 (Engine Main Relay) to B10 (Starter Engine Relay) and received 12v.

I pulled the codes P0606 (ECM/PCM Processor) which I believe is new. The code mentions replacement of the PCM or re-flash. I can easily re-flash with my latest ZZP tune but I am wondering when I last washed the car it caused issues. Any advice would be appreciated.

Additional Codes:

P1680 Control Module Accelerator Pedal Position (APP) System Performance- PCM
P1681 Control Module Throttle Position (TP) System Performance PCM

 

[Joebob]

Check the plugs at the BCM

 

[Desert Sasqwatch]

Phantom electrical problems are many times related to a ground being intermittent or missing. Check lug tightness, wire fraying (due excessive movement at a connection), and point to point continuity if possible.

 

[Gtstorey]

Check the wiring diagrams and see if there is a 12v feed or ground that the PCM, throttle body (throttle position module) and accelerator pedal.

Also wiggle all of the large connections at the ecm and bcm when it's doing this. The symptoms without the codes sounds like what will do occasionally and a kick to the plate over the bcm makes it start. I plan on trying an improved hold down on the bcm connectors this winter.

And don't forget, you could have more than one problem.

 

[Ross]

High speed LAN issues will lead to "loss of communication" messages between the 3 computer modules (BCM, PCM, Power steering), which you don't seem to be getting.

All 3 of your OBDii codes (P0606, P1680, P1681) have "Program the PCM" as the first step in the AllData DTC Testing and Inspection.

 

[ncgoblin]

Made some progress this evening.

Ignition wire shown in picture has continuity with A9 on C1 PCM fuse block (Engine Main Relay Fused Control). I jumpered A9 to B10 Starter Solenoid Crank Voltage and the engine started. When I try to start the engine with the ignition clutch and brake pressed I hear the relay click on the Fuse Block but the engine will not turn over. I also re-flashed the PCM and this appeared to fix my gauges so I am leaning towards this may have been another issue.

 

[ncgoblin]

Adding to this I am assuming Pin 5 is the one I need to be testing for sending crank voltage to the starter. This pinout goes to BCM C2 Pin 56 with 0.27 is the reading during continuity. From the BCM to PCM which connection should I be testing? I am thinking my initial test on A9 PCM C1 fuse block may be not a valid test.


Pin 1 Not Used
Pin 2 Battery Positive Voltage
Pin 3 Run/Crank Voltage
Pin 4 Accessory Voltage
Pin 5 Off/Run/Crank Voltage (WHT)
Pin 6 Key-in Ignition Switch

 

[Ross]

You are showing me the ignition switch connector? No this won't be sending crank voltage to the starter.
This page shows the circuit. Basically, the ECM decides on when to fire the crank relay coil, based on programmatic logic hidden in the ECM.
If the relay you hear clicking is the crank relay, then the purple wire going to the starter should go high (12V+).

The yellow wire from the ECM, C1, pin 48 will go low (12V-) when the ECM decides it wants the Crank Relay coil to click on.
If the 10A HVAC/IP IGN/PK3 fuse #10 in the BCM is providing 12V+ to the clutch switch pink wire, and that the clutch switch in closed, then the 12V+ goes on a different yellow wire (not shown below) to the Crank Relay coil. If the Crank Relay coil gets both 12V+ and 12V-, it should go click, sending power from the 30A Crank Fuse in the fuse block thru the Crank Relay to the starter. I would check the 2A BCM IGN switch fuse #8 too, just make sure it is good.

 

[Ross]

Opening this up to the forum, as you guys usually have good ideas.

To test if ECM is sending a low signal, you need to see if C1 pin 48 has ground. Put your electrical meter on Voltage testing, red lead on 12V+, and the ground lead on C1 pin 48. The if the ECM sends low to start the engine, the meter will read 12V, otherwise the meter will "float" probably showing 0V, but may wander depending on how sensitive your meter is, and how the ECM handles it. Might be easier to test with a 12V light bulb rather than a meter.

I followed your instruction and the result prior to turning the key to crank is 00.03v on the meter and when turning to crank no change.

So the ECM's isn't requesting an engine start when you turn the key.
I would think that would throw an OBDii code... so a mechanic can follow up.
Possible reasons that the ECM wouldn't request a start:
- the ECM is defective
- PK3+ key security issue
- not getting the clutch switch signal to the ECM
- not getting the key switch signal to the ECM
- the engine has a known OBDii error, like no crank signal, or something else that warrants fixing before starting the engine.
- high speed LAN communication issue
- probably lots of other things I haven't thought of.