Three seemingly unrelated electrical problems within a few days of each other is probably not a coincidence.

Any suggestions for troubleshooting from our auto servicing experts would be appreciated.

This is a 2001 GMC 3500 on the Savannah platform.

First problem, as mentioned last week, the voltmeter is reading way low.

Second problem, while holding a steady 70 mph on the interstate, speedometer dropped to zero, stayed there for several seconds, then came back up to 70. Only happened once, so far.

Third problem, truck has decided to go on strike. Will not start. Battery has plenty of cranking power, starter turns the engine briskly. Engine fires, runs for maybe a second, then quits. This truck is old enough that it does NOT use chip key, just old-fashioned plain metal key, like you get for a buck and a half at the hardware store.

Three different electrical problems within a few days of each other. I'll bet that there is a common cure for them all, but right now it's a total mystery.

This message has been edited. Last edited by: V-Tail,

So many connected electrical events happen through the start/run switch that it just makes sense to start there.

It's also a know problem area for a lot of GM products in that year window (someone who knows specifically could probably know if your model is one of them...I don't).

Checked with a friend of mine and he said there is a ground wire on the back of the engine block that will get loose or frayed. It will cause all kinds of weird lights on the dash and can shut the engine down. He said it is hard to see on the passenger side of the block at the very back.

It does sound an awful lot like a ground or connection issue. The PCM (engine computer) on these vans is also mounted in a spot (under the hood on the right side as you look at it from the front) vulnerable to water intrusion and rats building nests and chewing the wires.

Grounds (especially engine-to-chassis) can do amazing things. So can the ignition switch.

If you don't find a defective ground, I don't think it would hurt to add another ground wire between the engine and chassis.

After that I'd replace the ignition switch. Just replaced a bad one on a 2002 Olds (also GM) last Winter. Went from being an evil car to running like new.

Small block, big block or diesel?

You actually do have an antitheft system, it consists of the ignition cylinder and a security module, the key inside the cylinder creates a resistance value that the module has learned.

Possibly the module or ignition cylinder is bad, those years are notorious for Instrument clusters going out, I havent replace a speed sensor on any chevy's in recent years or ever that i can think of off the top of my head. Voltmeter reading low may be a bad alternator or see instrument panel above, they are rebuildable, and I have heard a guy on ebay sells them for a decent price.

Try the 30 minute learn procedure and see if it starts, Times are almost approximate, set a timer, dont wait 11 minutes, follow the instructions as close as possible.

30 Minute Learn Procedure
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds .
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 on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

Start the engine. The vehicle has new learned the PASSLOCK(TM) Sensor Data Code and/or password.
With a scan tool, clear any DTCs if needed. The history DTCs will self clear after 100 ignition cycles.

My '04 2500 Silverado had similar symptoms when the aformentioned ground cable let go.

Passenger side, top of motor, waaaay back against the firewall in my case.

Probably way back by the engine hump in a van.

I'd start there and then check the other big grounds up front.

quote:

Originally posted by gunnutty:
Checked with a friend of mine and he said there is a ground wire on the back of the engine block that will get loose or frayed. It will cause all kinds of weird lights on the dash and can shut the engine down. He said it is hard to see on the passenger side of the block at the very back.

This was my first thought, ground issues.

The grounds on the engine should be accessible after taking off the engine cover inside.

quote:

Originally posted by Jaywendland1981:

... Voltmeter reading low may be a bad alternator or see instrument panel above, they are rebuildable, and I have heard a guy on ebay sells them for a decent price. ...

He had a problem with this a week or two ago.

Above your left foot is a plug that plugs into the firewall. As you have been driving your left foot has loosened the plug. Check and secure.

Jaywendland: You asked "Small block, big block or diesel?" It's the V-8, five point something. 5.3? 5.4? 5.7? One of those. I can't verify right now, I had it towed to the shop where I have my vehicles maintained.

You mentioned possibility of bad alternator. Nope, ruled that out last week when I took it in because of low reading on the voltmeter. Shop owner checked with his diagnostic equipment; battery and charging system were all healthy. Voltmeter in the cluster was reading way low. I bought a digital voltmeter, cigarette lighter plug-in type, and it shows normal system voltage, so the voltmeter in the cluster is giving a false low-volt indication.

As far as security, resistance value with key, there are four keys. Several drivers, each has his own key, plus a spare. I rounded them all up, and the failure to start is exactly the same with each key. Starter turns briskly, engine fires, and then dies within a second or so.

Question on the 30 minute learn procedure: you said "Observe the SECURITY telltale." What is the "SECURITY telltale?" I have had this truck for maybe ten years or so, I do not recall any SECURITY indication, ever.

Royal pain in the ass. I need to get back on schedule for re-supplying my customers.

I have a similar van. I have had the coolant temp sensor wire and one injector wire break on me. It would be intermittent at first as more of the strands of wire broke it would fail completely.

My guess is the way the engine is situated means more heat buildup which is not good for the wiring.

Somewhat tricky to find because the wire insulation looks fine even though the wires are broken.

As mentioned above the clusters have issues.

Also as mentioned check all grounds.

Does the Service Engine Soon light come on when you turn the key to the ON position?

Should grounds be ok, check all fuses.

Since it fires momentarily each time you try and start the engine, this suggests there is some fuel getting to the engine. A fully failed fuel pump will, after residual fuel is gone, just crank without firing. However, fuel pump or fuel pump circuit may still be an issue.

On some vehicles, the manufactures put a strategy into the computer to run with the Mass Aiflow Sensor disconnected. If your MAF or MAF circuit is faulty, or the sensor is extremely dirty or plugged, the symptoms you describe can happen. Try disconnecting the MAF sensor and try starting the engine. If the engine runs, then you have a direction to follow.

The Security telltale mentioned is probably the word Security flashing in the square message screen in the cluster.

Similar issues when I had my 01 Silverado. Turned out that the trailer pigtail had corroded and shorted. Cut the plug off and taped the wires up to get home, then installed another plug.

The instrument cluster issue is likely unrelated to the starting issue. The little motors work, don't work, work too little, and work too much at their whim. The only fix is to have the entire gauge cluster rebuilt.

I'm going to go with fuel delivery problem on the starting issue.

2001 C-K pickups and G series vans have a security system but it is not key related, it is a sensor built into the ignition lock cylinder case and a magnet inside the actual lock cylinder. If your key has a internal sensor the chrome shank just below the round plastic head cover would have either the designation "PK3" or a circle with a "plus" mark in the center. No reprogramming necessary when replacing those keys without the marks. Ones with those marks have two different procedures, the "add a key" takes thirty seconds or about the time frame of the seat belt warning chime X2. The fun ones are when the customer loses all of their keys, then it takes a hard relearn of one half hour with three on and off cycles of the key spaced ten minutes apart. Turn the key on and leave it on for ten, turn off, turn right back on same procedure three times. Should start then. But again, you should not have to concern about that. IIRC the only other option for the G series was single key locking, an SEO order. This would be for fleets, same key code for as many vehicles as they would order. Makes it easy when one driver loses his keys...........

The lock cylinders do fail though even there is no mechanical connection between the component. There is a relearn program once you replace that cylinder and or case but since I have left GM dealership employment as of the end of June my access to the factory manuals has been ended. Your local library may have a program called AllData, this is online service manuals, try them.

The cluster is a known problem at least in the pickup and suv lines.. My 2004 Sierra was on it's 4th one at 155K. I don't recall if the TSB regarding the stepper motors in the cluster being faulty also affected the G series trucks as van based vehicles were a rarity at the last dealership I was at.

You should be able to call your local dealership, again they can search the bulletins in GM Dealer World system to see if yours is affected. Another person brought up grounds issues, again C-K's had that problem, it affected the hour meter and caused it to reset to zero hours.

Also, another problem, that era G series had the PCM (Powertrain Control Module) inside the engine compartment, problematic for corrosion issues and I imagine the salt air is as bad on them as moisture and salt residue up here. Our extreme cases around here the PCM will swell up from the reaction between the salt and the cast aluminum case of the PCM and corrosion would migrate back up the engine wire harness towards the passenger compartment.

And be warned that the PCM must be programmed to the vehicle at replacement time, not a backyard do it yourself job. And at least in the GM Parts system a compromised or damaged PCM outer case or one that has any sign of moisture intrusion or without the GM tag with the part number is not eligible for the core charge return.

Id bet on a bad ground