94burb

So my 2007 200k Suburban which has been running great, suddenly decides to not crank after work the other day. It was cold so I figured maybe the battery was shot. A quick jump from a friend and headlamps never dimming said otherwise. Towed it home and did a few tests. First was neg connection on the starter and pos power on the main solenoid post.... all good. Next the relay... tried to jump it with a wire and I got nothing (relay did make a soft click noise when key is in the start position). Dropped in a NEW starter and did a relay jump which now turns the starter over but would not start with key in run position. put the relay back in place and with key on, jumped the pos starter post to the solenoid post and it cranked and started. Just trying the key start still has no crank, just the relay click.

No engine codes, no weird lights on the dash... all looks good. tried to start it while moving the shifter but still nothing. The security light goes out with all other indicators a few seconds after the key is powered on. Everything works except the connection to the crank position!!!

At a loss here and could use some help please

Thanks!

tech2

the starter relay is clicking but is the starter solenoid clicking?...if not....you need to check the solenoid signal wire from the relay. power out of the relay goes to a starter fuse 40 amp in the u nder hood fuse box. this fuse is only powered when the relay closes. if the fuse is powered on both sides in start...check the power at the solenoid purple wire with thekey in start.

94burb

when I jump the relay in the fuse box, its activates the stater as it should. Something is blocking the stater from cranking via the key ignition but yet the starter relay is getting power from the key ignition. I used a test light in the relay and it lights up every single time I turn the key to crank! After screwing around with the relay and jumping it for tests, somehow it started via the key.

The next morning it was approx 30 degrees out and it again NO CRANK... turned the key for about 5 attempts and it started, Not sure why but it did. Took it to work, started it perfectly at Noon and at 4 pm, parked it home and never touched it until this morning which again was about 30 degrees out. 1st attempt was NO CRANK... 2-20 attempts, still no crank. I jumped the stater solenoid and it starts fine. Jumped in and drove it to work.. 10 min ride on the highway. Thinking its now warmed up. I attempted a start in work parking lot and its NO CRANK again, ugh. I will test it at lunch today.

QUESTION for today is... the Pos battery cable splits: 1 to the starter, 2 to the firewall where itt splits the cable again. WHERE does those 2 splits go to?

94burb

started perfectly at lunch today! warmer now.. aprox 50 degrees. started and shut off multiple times without a glitch, even when using factory auto start.
I am starting to think its temperature related. Battery is only 1 year old and has plenty of juice to keep head lamps perfectly bright during all my testing.

I will have the battery tested tonight just in case

Any other suggestions?

Cusser

Always a good first step, to test under load.

repairman54

I'd check the underside of the fuse box for poor connections and discoloration.

94burb

so the weather has been above 30F the last few days which allowed my engine to start instantly every time. the battery was pulled the other day and put under the toaster like tester for a good 30 seconds and it held strong at like 600 CCA.

I will have to wait for the 30s to hit again before I can test the battery again. If I can eliminate the battery, that leaves me with the ECU being faulty.... Does anyone else agree?

tech2

nope. if the starter solenoid was engagingwhen the fault was occuring...the pcm is doing its job.
How did you load test the battery?
loose connections is another possiblility. this can be checked by doing voltage drop tests across the insulated and grd circuits from the starter to the battery.

94burb

No, the starter solenoid never engages when the key is in start.... on the original starter and also on the new one. The relay in the fuse box does signal power when the key is turned to Start, and when jumping the relay ports with 2 wires I can get the starter to CRANK.

What I am noticing now is that all is flawless when its approx 40 degrees or warmer. When colder I get a NO CRANK but power to the relay fuse. The pic attached is what I used to test the battery. in about 45F weather. Not sure of the device's tech name but I call it "the Toaster".

tech2

if you have no power to the starter solenoid do what i said in the first post. report if no power to the purple wire key in start