How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Gary Your Own Question
Gary, Technician
Category: Car
Satisfied Customers: 17155
Experience:  GM master tech for 15 years/ASE master tech for 20 years
Type Your Car Question Here...
Gary is online now
A new question is answered every 9 seconds

Hummer H2: Hi, I have a 2003 Hummer H2 with 200k miles. The

This answer was rated:

Hi, I have a 2003 Hummer H2 with 200k miles. The truck cut out in the entrance to the gas station, I rolled up to the pump but after adding gas truck wouldn't crank with all the symptoms of low battery.
Here is a list of things I did after:
Tried jumping it, no change.
Tested the Optima Yellow Top batt, good.
Jumped the starter motor, engine cranks but no start.
Tested all fuses, good.
Tested starter and ignition relays, good.
Jumped the starter relay, engine cranks but no start.
Tested starter relay socet 86, no ground during crank ecm is not sending crank signal.
Tied reading OBD2, connection error.
Tested pink wire of ignition switch, powers on in pos. 2
Tested 2 pink wires to the ECM, hot when key in pos. 2
Tested all ground wires to ECM, all good ground.
Changed ECM for new one programed to my vin, no change.
Programed PassLock, no change.
Run PassLock test from manual, good.


FixItMan : Hello, and thank you for letting us help you with your automotive question. Just to clarify, right now the engine does not crank?
Customer: Not with a key.
FixItMan : I'm not sure what you mean. What does the vehicle do right now if you try to start it?
Customer: Exactly
Customer: Dash lights up, I turn the key and everything dies down till I release the key.
Customer: Off for the weekend...? Opt- out....
FixItMan : Sorry. Having connection issues. Did you still want help?
Customer: Yes
Customer: Weekend is the only time i can work on it.
Our chat session just would not work. Let's try this. It sounds like you either have a bad ignition switch or a problem with the vehicles power supply. You may have corrosion built up in the positive battery cable to a problem at the connection to the fuse panel. Have these items been checked?
Customer: replied 4 years ago.
What?!!! Coroded battery terminal!!!! You sure it's not my door mats? WTF did you read the question at all?
I am not sure if you read my answer correctly. I did not say battery terminal. I said inside of the batter cable. It is common to get acid inside of the cable, which will cause corrosion, which will cause resistance, which will cause a voltage drop and a loss of amperage. If this is how you plan on trying to get this vehicle running I will opt out and allow you to work with someone else.
Customer: replied 4 years ago.
Please do opt-out.
Customer: replied 4 years ago.
O and thank you for waisting 5 hours of my Sat.

new expert here did you still need help ?


Customer: replied 4 years ago.
ignition key on the check engine light is lit up in the dash cluster ?
does the horn work ?
if you put your meter on the big power wire that connects to the under hood fuse box what does it read for volts?
then when holding the key to crank what will that big power wire show when holding the key to crank ?
im sorry for the 20 questions but i want to be sure to give you the correct answer
Customer: replied 4 years ago.
Don't be apologetic, questions eliminate stuff, I'll try it now....
ok let me know
Customer: replied 4 years ago.
Check engine light dose not come on at any time.
Passlock light comes on and goes out 3sec after turning the key, then comes back one minute later and stays solid lit for 15+ min.

Big wire under the main fuse box in the engine bay gets 12.00v when key is turned to start position v drops to 11.88v
ok so when the ignition key on there is NO check engine light lit up on the dash cluster ?
Customer: replied 4 years ago.
No check engine light at any time, might have some thing to do with OBD2 scanner connection error that i mentioned in my original question...
ok with the key on in the under hood fuse box can you see if the fuses called PCM1 and PCMB show 12 volts on both sides of those fuses testing threw the little opening in the tops of those fuses inplace see if both show 12 volts on both sides of each fuse
Customer: replied 4 years ago.
Key in position 2...
PCM1 fuse 0v at both prongs, fuse good.
PCMB 12v at one, Bad fuse... Swapped it out for good one and tried to start the truck..... Engine started to crank but no start, i tried cranking again and now no crank, fuse still good with 12v
Customer: replied 4 years ago.
Progress owsome! :)
can you see if PCM1 will have 12 voltas both sides when cranking ?
is the check engine light on now when the key is on ?
Customer: replied 4 years ago.
Ok, truck cranks now 9 out of 10 tries,
PCM1 is 0v all the time... Position 2 and crank position.
Check engine light is on now and OBD2 connects good, no codes though.
Customer: replied 4 years ago.
Maybe try to learn passlock now again
when cranking is the theft light on or blinking ?
it bothers me that PCM1 fuse has NO power on either side when cranking or the ignition key on
Customer: replied 4 years ago.
Now it is, passlock light blinks when cranking and the fuel pressure is 0.... Sounds like anti theft system kicked in...
ok before you do the relearn i want you to check ALL the fuses visually one at a time and make sure NONE are blown
now do you have the old PCM still ?
Customer: replied 4 years ago.
I do have the old one.
ok put in old one and see if you get fuel PSI and make sure ALL the underhood fuses are NOT blown
Customer: replied 4 years ago.
Ok all thE fuses visually inspected in both boxes, all good.
Installed the old ECM and..
no fuel pressure
Pcm1 still at 0v
Crank but no start
Obd2 connects but no codes found.

The other I just noticed that the fuel gauge is not working.
ok try the relearn next and lets see what happens
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to start the engine, then release the key to ON, vehicle will not start.
  3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
  4. Turn OFF the ignition, and wait 5 seconds .
  5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes , the vehicle is now ready to relearn the Passlock(TM) Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK. IMPORTANT: The vehicle learns the Passlock(TM) Sensor Data Code and/or password XXXXX the next ignition switch transition from OFF to XXXXX must turn the ignition OFF before attempting to start the vehicle.
  6. Start the engine. The vehicle has now learned the Passlock(TM) Sensor Data Code and/or password.
Customer: replied 4 years ago.
Customer: replied 4 years ago.
Passlock light went out after 5 sec and it didn't came back, I'm 5 min in to the first step..
ok so its more than likey learned already
let me look over a few scematics
in the mean time pull out the fuel pump relay and when you are holding the key cranking can you see if 2 terminal that the fuel pump relay goes into shows power when cranking
Customer: replied 4 years ago.
Fuel fuse good 12vFuel relay 87 has 12vCan you clarify, relays are up side down in my truck.

ok so 2 terminals show 12 volts when holding the key to crank ok

do me a favor put the fuel pump relay back in and remove the ignition 1 relay turn the key on and how many terminals show 12 volts ?

Customer: replied 4 years ago.
No only one #87 shows 12v...

if you turn the key off will that 12 volts go away ?

Customer: replied 4 years ago.

Customer: replied 4 years ago.
Ignition relay working properly.

ok so that shows the ignition switch is working the problem being we are missing the power to one of those terminals that should be power all the time and it gets it internall from inside the under hood fuse box

lets confirm the big power wire into the fuse box shows 12 volts.inside that fuse box its supposed to get that 12 volts to another terminal

lets try this.put the relay back in and jump 12 volts to the PCM fuse that had NO power at any time remember key on key off cranking ect..there was one PCM that showed nothing and the fuse was good.with a wire jump 12 volts to that fuse and see if the fuel pump will work and if it will start

Customer: replied 4 years ago.
Ok will do , FYI I piled a plug and there is no spark...


that fuse PCM is power by that ignition relay it appears we are missing the power from inside the fuse box to the other leg of that relay to power up the other PCM stuff

Customer: replied 4 years ago.
Ok i jumped the PCM1 fuse to the battery and the engine went through its usual (now days absent) routine of clicks and noises then i cranked it and it started!!! But when i puled the key out of the ignition it stayed running till I puled the jump off.

Now i remember that few days after the breakdown the engine would still go through the clicks and noises routine but wouldn't crank...

ok the problem is that under hood fuse box is bad it is not sending 12 volts from the big power wire from the battery to that relay. If the wiring looks good under it replace that under hood fuse box and it should be fine

good work by the way testing everything !

Gary, Technician
Category: Car
Satisfied Customers: 17155
Experience: GM master tech for 15 years/ASE master tech for 20 years
Gary and 6 other Car Specialists are ready to help you
Customer: replied 4 years ago.
I'll let you know if it work out, thank you.
Customer: replied 4 years ago.
It was the fuse box. Thanks

any time!

good job

thank you for using Justanswer !

happy holidays!

Customer: replied 4 years ago.
Hi, I just noticed I have a subscription for another month.... Might as well milk it....

Truck is running fine minus one small detail. Anything with a light bulb in it pulses when the truck is on, regardles of rpms or speed the truck is moving with.
Did clean to metal grounds... Under driver door, on frame under driver headlamp and under hood next to brake master cilinder culdn't reach back of the block. Changing alternator had no efect on the problem.
just open up another question with this concern stated