1998 c1500 starts then stops instantly

I work in a automotive garage and am having a problem with this truck. It starts then stops instantly, I scanned it and know it is the security feature shutting it down. I have done my homework and found I have to bypass the passkey system by measuring the resistance between the yellow and orange/black wire at the tumbler. I did this and got 33.2, I got a resistor and soldered it in and the vehicle does the same thing.

I have no Idea what to do and need some help. History on this vehicle is it sat with a dead battery for the last year and a half, i don't know if this is relevant. also i was told all I should do is connect the yellow wire straight to the black wire, anybody here of this?

any and all help appreciated, thanks..

Did you measure the resistance with the ignition on and the yellow wire cut? (measuring the key side of yellow wire after you cut it). 33 ohms is very low....

yes I did test it with the ignition on. It also did not change during cranking either??

Check your Private Messages.

NOTE: below is from a thread I posted a couple years ago:

My truck (98 Silverado) pissed me off for about 3 months, occasionally doing the same "tamper mode" thing. I tried to use my remote start (or my ignition key) and it wouldn't start, I waited five or ten minutes, and then it started right up.

Finally, I got ambitious and did the permanent bypass on the security wire. I found some instructions on the web. I cut the yellow wire, then measured the cranking ohms resistance at 577. Then off to Radio Shack, where they had 560 ohm resistors +/- 5%. I bought a pack of five for 99 cents. I measured the resistors to find the best one. Closest I could get (to 577) was 554 ohms, so I soldered that one onto the yellow wire (processer end) and into the orange/brown wire.

The instructions said I needed to be within 1% to 2% on the ohms. I was more like 4% off the 577, but the truck fired right up with no problem.

That was over 2 years ago and the truck has worked perfectly ever since I soldered in the resistor. I fixed the problem for about two dollars in parts!

Here's a diagram showing what I did:

http://csgbenefits.org/vats2.jpg

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Chevy-SS (http://www.automotiveforums.com/vbulletin/member.php?u=275744) that's the post that I read and tried already. that's where I got a reading on 33.2 or 332ohms. I tried a resistor and a pot that was adjusted exactly to 332 but the vehicle still starts and shuts off immediately and I cannot figure out why.

a stupid question, car thieves steal these chevy trucks all the time and quickly, what the heck do they do to bypass the security so fast , they don't solder any resistors or anything, I wonder what they do???

To take your mind off of the security system for a minute, check this:

Start the motor and when it dies leave the key in the run position. Check for batt voltage at, and thru, these 3 fuses in the underhood fuse block:
1. IGN-E
2. ECM-1
3. ENG-1

Post back findings.

i'll check that and post back what I find tomorrow..

Sorry for taking so long to post my findings, had a family emergency and left town, didn't get back to work till today. I checked the power to all those fuses and they all have power running through them.

Also I checked the red/white wire going to the ignition and my wire schematic said it should have 12 volts but I get no power whatsoever. could this also be a problem?

I work in a automotive garage and am having a problem with this truck. It starts then stops instantly, I scanned it and know it is the security feature shutting it down. I have done my homework and found I have to bypass the passkey system by measuring the resistance between the yellow and orange/black wire at the tumbler. I did this and got 33.2, I got a resistor and soldered it in and the vehicle does the same thing.

I have no Idea what to do and need some help. History on this vehicle is it sat with a dead battery for the last year and a half, i don't know if this is relevant. also i was told all I should do is connect the yellow wire straight to the black wire, anybody here of this?

any and all help appreciated, thanks..


I would check for the fuel pressures...you could have 2 problems as this vehicle has been sitting for a long time and fuel made in these times don't like this.............!

Sorry for taking so long to post my findings, had a family emergency and left town, didn't get back to work till today. I checked the power to all those fuses and they all have power running through them.

Also I checked the red/white wire going to the ignition and my wire schematic said it should have 12 volts but I get no power whatsoever. could this also be a problem?

The check on those 3 fuses was to check power coming out of the ign sw. So from your post it appears the ign sw is good.

I looked in my '98 (2nd edition) schematics and could not find a red/white wire in the ign system? Two red wires feed the ign sw and a pink wire feeds the 3 fuses from the ign sw. Fuse "ECM1" feeds the VCM, ICM, CKP & coil all thru a Pink wire. I suspect my manual deals with later model 98's into the '99 crossovers (old body style).

Where does your schematic say the 12v should be coming from on the red/white wire?

332 ohms? I don't want to piss you off anymore than you probably are, but you did measure this with the yellow wire cut and cranking the engine? This must be the cranking resistance..Mine is 595 ohms.. Is the security light on? If so is it flashing?

332 ohms? I don't want to piss you off anymore than you probably are, but you did measure this with the yellow wire cut and cranking the engine? This must be the cranking resistance..Mine is 595 ohms.. Is the security light on? If so is it flashing?


Yeah, I agree with this. I think you should re-check the resistance, while cranking.

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The check on those 3 fuses was to check power coming out of the ign sw. So from your post it appears the ign sw is good.

I looked in my '98 (2nd edition) schematics and could not find a red/white wire in the ign system? Two red wires feed the ign sw and a pink wire feeds the 3 fuses from the ign sw. Fuse "ECM1" feeds the VCM, ICM, CKP & coil all thru a Pink wire. I suspect my manual deals with later model 98's into the '99 crossovers (old body style).

Where does your schematic say the 12v should be coming from on the red/white wire?

Sorry I wasn't clear enough, I meant the red/white wire that goes to the anti-theft doesn't have 12v.

i did check fuel pressure earlier and ended up changeing the fuel pump because it only had 22 pounds pressure, so it is now good.

I rechecked my resistance and it is still the same but does not change whether the ignition is on or in crank mode.

I found out some intesesting info on this vehicle which makes me want to quit on it. The reason it sat for so long is because it fell through the ice and was submerged for many hrs. If I knew this prior I wouldn't have tried to fix it in the first place.

OK. I found the RED/WHT wire. It runs between the Passlock module and the Passlock Sensor (in the steering column). Can't tell where the 12v should be coming from but my guess is the Passlock module to the Passlock sensor. I suspect the module or the sensor is fried or there is an open in this circuit. There is a connector C266 (Part of the IP harness to the steering column harness, to the left side of the steering column, near the bulkhead) that has 35-40 wires going thru it. This circuit is one of those wires.

Sorry to hear about the submergence. Most likely other issues will thaw out as well.

Also post back any and all Passlock DTC's

Good Luck.

I found out some intesesting info on this vehicle which makes me want to quit on it. The reason it sat for so long is because it fell through the ice and was submerged for many hrs. If I knew this prior I wouldn't have tried to fix it in the first place.

this may be a correct path to take, over time this vehicle will drain you..

Chevy-SS, your post and solution was RIGHT ON! Solved my problem for 99 cents. Dealer quoted me $700. Thanks:runaround:

Chevy-SS, your post and solution was RIGHT ON! Solved my problem for 99 cents. Dealer quoted me $700. Thanks:runaround:



Yeah man, nice work! Glad I could help.

It feels pretty damn good to save $700, doesn't it? :iceslolan



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$3.26 @ Radio Shack and no more blinky blink light. Thanks for the info!!!

$3.26 @ Radio Shack and no more blinky blink light. Thanks for the info!!!


I'm still following this thread. My '98 K1500 is still starting up just fine. Glad to see you got your problem solved for short money!!! :biggrin: