Crazy gauge readings, wrong shift points... Speed sensor?

[FerrioloM]

Hey guys,
My dads 2000 Chevy Express Van (5.7) sat for a few months and then started doing some crazy things.

The gauges read whatever the hell they feel like. Speedo runs like tach, the tac bounces all over gods creation, no ABS light, but everything else flashes on and off or just stays on.
First I thought was a speed sensor, as I've read it was a fairly common problem with these vans.
My only other idea was maybe the PCM took a dump on him? But wouldn't that throw a code? The car is throwing no codes, and shows no CEL.

Any help would be greatly appreciated!

[DFBonnett]

Check the battery voltage. If that is OK, I'd pull the engine cover off and inspect for wiring damage by a rodent during the time the van sat. BTDT.

[MT-2500]

If the battery was dead and jump started?
Check that it has charged back up and charging system is working good and cabels are good and clean.
Also disconnect neg batter cable and hooh it back up and see if that helps.
MT

[FerrioloM]

It's not related to the charging system/battery.
Where is the relay box? Specificially the ABS relay?

Thanks.

[MT-2500]

As in upper post disconnect neg battery cable and hook it back up.
Let us know if that helps.

[FerrioloM]

Heres what I've done:
Removed neg cable of bat and turned key to start for 30 seconds (flashed ECU) No change.
Replaced speed sensor on the tranny. No Change.
Checked all wires under hood and from the VSS. They all check out fine.
I think the problem may be related to the ABS switch/sensor/relay so if anyone knows where any of them are that'd be great. The fuse box under hood says "ABS Export" but theres no relay there?

[MT-2500]

Originally Posted by FerrioloM

Heres what I've done:
Removed neg cable of bat and turned key to start for 30 seconds (flashed ECU) No change.
Replaced speed sensor on the tranny. No Change.
Checked all wires under hood and from the VSS. They all check out fine.
I think the problem may be related to the ABS switch/sensor/relay so if anyone knows where any of them are that'd be great. The fuse box under hood says "ABS Export" but theres no relay there?

The abs system is fused.

[FerrioloM]

So there is no relay. Damn... any other ideas as to what is going on? The tranny fluid is pink with no stink. Could it be an ABS wheel sensor? Is there anyway to pull a code to determine why the abs light is on or if it is even relevent?

[MT-2500]

ABS capable scanner is the only way to get abs codes.
Might pull dash and check wiring and plugin and groundsand power feeds.
Check with your dealer for tsb and problems on gauges.
Good Luck

[MT-2500]

Check all voltage and grounds to dash gauges.
There is a voltage check in a factory repair manual for testing dash gauges and wiring.
Or .
http://www.alldata.com/products/diy/index.html

[FerrioloM]

I will but it isn't like the gauges aren't getting the correct voltage because the shift points are fubar'd and the odometer spins in correspondence with the speedo. Like its adding miles really fast because it thinks I'm going 100 when the truck is doing 20. Then it tries to shift into OD and every other thing. The speedo is jerky and surges. It's very odd.

[MT-2500]

If all gauges are acting up it has a voltage problem in dash or to it.
A good engine/transmission capable scanner can check and test the gauges and the speed sensor reading to dash and PCM.
Good Luck

[MagicRat]

Originally Posted by MT-2500

If all gauges are acting up it has a voltage problem in dash or to it.

It may also have a poor ground to the instrument cluster.

[MT-2500]

Originally Posted by MagicRat

It may also have a poor ground to the instrument cluster.

MagicRat
A big 10-4 on the ground.
A bad ground will do a lot of starnge things.