I thought it best to include everything. Even if many of them are not applicable. Truck is '98 Jimmy 4.3, 4 door 4X4. Please excuse my choppy style. I was typing things as I was thinking and I may have missed a pronoun or a verb here and there.

CEL on and off once a week for months. I thought it may have to do with my holey muffler, replaced, then no CEL for weeks.
Security started coming on random no effect on operation, they go off by themselves.
Fog light installation. Run harness from battery, through firewall, rocker switch added to dash
Week later, CEL on for first time since muffler. Security light more freq, still no effect.

Started truck, Instr. Cluster lights out, Batt warning on, no fuel level and no Temp gauge. No indic lights on 4x4 buttons. Truck still ran and I needed to go places, so I drove about 100 km + - while waiting to connect with mechanic.

On startup few days later, less than 1 sec, all power went, key locked in ignition.
First guess – battery drained because not charging while driving. Can't tell without gauge. Got tester and charger ready. Showed 12.4. Put charger away for now.
Found scanner settings to check, but way technical for me. Anyway, scan port inoperative cos no power.

Second guess – Security shutdown due to driving with instr panel lights out. Research suggested fuse. Checked all fuses in DS panel.

Next suggestion was reset computer, so I removed Neg cable for 1 hr. Started as normal for 1/2 sec, then shut down as before. Like a relay snapped open. As I was removing neg cable, there was electrical-type sound coming from engine, like solenoid. So I know there's juice getting to some part of the system.

The new fog lights are also inoperative. Starting to wonder if two weeks ago fog light install may have started something, but I'da thought problems from that would have already shown up.

Any thoughts or suggestions, anybody? I'd like to get mobile at least, so I can drive to my mechanical guy.

 

There are a lot of moving parts to this problem, there may be more than one issue.

if all of this started after the fog light install, I would uninstall that first. Disconnect the wires that interface with power and put the power circuits back to original.

You can’t read codes because there is no power to the ODB socket? If so have you checked the fuse that powers the socket and the power coming into that fuse?

The truck starting and then stalling may be the engine computer defeating the fuel injector pulses due to a security issue. The next time it won’t start but will crank we need to find out if it’s fuel, spark injector pulses or timing. Travel with the ability to measure spark and fuel pressure and do the fuel pressure sticky test now.

When you say the dash goes out is this just the illumination bulbs or the gauge functions?


George

 

Thanks for chiming in George. I'll get those suggestions underway later today, after the rime of frost on the truck has melted.

First, though, some clarifications.

Disconnect the wires that interface with power and put the power circuits back to original.

Will unhooking from the battery do that? I didn't do the installation, so I don't know how power circuits may have been altered.

Is the fuse that powers the OBD port the same one that powers the instrument cluster, ie: cigarette lighter fuse? Or numbers 2, 4, 11 or some other? If so, I pulled each fuse in the DS panel and they all look good.

...the engine computer defeating the fuel injector pulses due to a security issue.

I think the answer lies in this direction. I also think you're right about more than one issue.

However - starting and then stalling, won’t start but will crank – this is not what I meant. After one hour battery disconnect, when I said: Started as normal for 1/2 sec, I meant that the dash lights came on, or more accurately flashed on, then went out. Didn't get as far as cranking. Say, under 1/4 sec.

When you say the dash goes out is this just the illumination bulbs or the gauge functions?

All of them. No gauge readings, key locked in ignition, shift selector frozen, no lights anywhere, head lights, fog lights, dome lights, dashboard lights, nada. As though the battery was out of the truck.



I'll check back later this evening with results of whatever I was able to do.

 

The fuse for the data port is Cig LT fuse 2 in the IPFB.

OK, I misunderstood what is happening here. I don’t how to remove the fog lamps from the system because I don’t know what was done so do the best you can. It sounds like you have catastrophic power loss in a dozen circuits. If that’s what is happening then we need to find out where the fault is. The ignition switch powers a bunch of stuff in more than one circuit so this is a prime suspect. That said, the job is involved so we need to confirm that it’s the ignition switch and if not, where is the problem. The next time you get a catastrophic power loss leave everything as is and start probing with a voltmeter on 20vdc:

What is the battery voltage at the battery terminals
The voltage coming into gauges fuse 4 ipfb
the voltage coming into ECM1 fuse uhfb
the voltage into the cluster fuse 11 ipfb
he voltage into the RDI fuse 19 ipfb


George

 

Okay. I printed that and I'll do those tests. I did disconnect the power line from the battery without effect. He had tied in at the + terminal. Does that sound right?

 

If a circuit was added directly to the battery it needs to be fused.

George

 

I'm starting to think that I need an exorcist. Yesterday, I detached the – terminal and left it overnight. Early this afternoon, I did some tests. Before reconnecting the battery, I tested for Ω and got 0.0 for everything on the list.

Then I reconnected the battery and tested for volts: 0.0 down the line.

Then I turned on the ignition, retested: same results.

Just because, I tested the resistance again:
2=0
4=.6
11=.4
19=6.0
ECM1=.16

Then, I figured “nothing to lose” so I turned the key to Start and to my total surprise – it started up. Checked the fuses again... no change.

I'm going to let it cool down, then see if it still starts. If it does, I have only to find the cause of (as reported in my first post) the cluster lights out, batt warning on, no fuel level and no temp gauge. No indic. lights on 4x4 buttons. The fog lights are still disconnected.

At least, I'll now be able to plug into the scan port.
I'll be back.

 

What are you measuring the resistance of? The fuse itself, the wire from the fuse terminal to the load?

Yes all voltage measurements are with the ignition in the run position, meter in 20vdc, black meter probe to battery negative post, red probe to test point. Explain where the meter probes are going for those measurements?

George

 

Probes were on both pins of fuses. Probes don't have enough reach to get from battery to fuses.

 

We need to back up and talk about basic measurement techniques and then take another look at your truck:


SOme definitions:

Voltage is potential, the potential to provide current at a specific level of resistance. The higher the voltage, the higher the current flow and hence power for a given electrical resistance. A municipal water tower provides a good analogy. Voltage is the same as water pressure potential. The higher the tower and the larger the tank, the higher the water pressure potential. The diameter of the water output pipe is the resistance and the water flow rate is the current. The larger the pipe then the lower resistance and again the higher the water flow. The converse of these things is also true. The equation that describes this is ohms law: V=IR, voltage equals current times resistance or I=V/R. Lower resistance or raise voltage and current goes up.

Power is current times voltage or P=IV. Raise voltage or current and power goes up.

Resistance measurements:

Resistance is measured from one side of a component to another side of a component, usually disconnected and isolated with no power applied or involved. If you measure resistance in a dc circuit with a simple resistive load like a wire or lamp bulb it is called resistance. If you are measuring an inductive load like a motor winding it is called impedance which takes into account the changes in value due to frequency changes and inductive load behavior. The scale is in ohms. Continuity is a subset of resistance and is a meter setting that beeps at you if the resistance between those two points is low enough to indicate good connection or continuity between those two points. In the absence of a continuity tester you just measure ohms of resistance on the lowest scale setting of your meter. We use this to check if a removed fuse is blown or if both ends of an isolated wire are connected together with almost no electrical resistance, the resistance to current flow.

Voltage measurements:

we almost always measure the voltage at a single point with the positive red meter probe, with reference to battery ground. I usually say battery ground because it is the most error free way to measure voltage. You can also put the black meter probe on a frame point but you have to make sure you have solid contact to shiny clean metal or the readings will be corrupt. You can measure voltage across two points not involving battery ground like both ends of a fuse but this is a very specialized measurement that we will not use very often here. That particular example would be used to measure the voltage drop across a fuse to look for parasitic current draw when the truck is turned off which is not what we are doing here.

Current measurements:

Current is measured in amps and is the rate of the flow of electrons through a load and along it’s wiring. You either place the meter inline in the actual circuit or you put a precise 1% or better low valued resistor inline and measure the voltage drop across that resistor to calculate current with I=V/R. You can also measure current with an amp clamp around a wire in the circuit. Cheap ones will measure AC current only, better clamp meters can also measure DC current flow. These are less accurate, especially at low current levels.


So to measure voltages 90% of the time it’s circuit energized, meter is 20vdc mode, red probe on the measurement point and meter black point on battery or frame ground.


George