2001 Chevy 4.3 Blazer Trany stays in 2nd & speedo @ zero

[carriedi]

I have a 95 blazer 4.3l vin code W. My TCC does not come on. I can turn it on with a scanner buty it never comes on by itself. Since I can turn it on by commanding on with the scanner wiring should be good. Trans temp runs about 175F and TPS works normally when I look at the TPS on the scanner in engine controls. Tried a rebuilt vcm (located over coolant bottle on passenger side engine compartment) Had it flashed at dealer. No help. What am I missing here? Scanner always shows TCC forced off. any ideas or has anyone had similar problems like this?

Thank for any help you can give me.

[TerryAuto]

Any trouble codes?
About the only other thing that can prevent TCC is a brake switch applied signal.

[carriedi]

no codes. Had a c1286 in ABS, (bulb was out) fixed that and cleared code. no other codes in any modules. brake switch appears to work normally. Cruise control turns on and off. Purple wire

[TerryAuto]

Hmm. Very strange. Since you can control it with scanner, then the VCM and everything past it is good. Something is inhibiting TCC. Vss signal, A/C clutch engage signal, 4wd H/L signal.

[carriedi]

as it turned out the pwm solenoid amp draw was very low. changed the solenoid and now it is working normally. I don't know why the computer didn't set a code. or why I could command the computer to turn on the solenoid and it would work. But it's all working now.

[stillfishing]

I have a 1997 Blazer that will not switch from 4H to 2WD. I push the button and the light flashes in the switch and I can hear a relay clicking in the dash, but it will not change to 2WD

[carriedi]

when you first turn your key to the run position what do the fwd indicator lights do? do they all blink once and then the 4wd indicator comes on and stays on or does it do something else? do you have the indicator in the dash for the front axle engaged on too? that would be for the vacuum actuated front axle engaging collar

it is common for the transfer case shift motor to go bad.

[roy33]

The speedometer stays at 0 all the time. When the transmission is in drive it won't come out of 2nd gear. I replaced the VSS on rear of tranny. Same problems. I had a burnt harness near the ECM unit. Rewrapped all wires. Still no speedo or shift. Still searching on the web for answers. Any help would be great.

[carriedi]

you should hook up a scanner to your truck and look at codes that would put your trans into limp mode. Verify that you have a good VSS signal when the vehicle is moving. If you show the normal speed on the scanner but the instrument cluster reads nothing then you need to look and the cluster and the wiring to the cluster. If you don't have a vehicle speed sensor reading (sensor reads zero) while the truck is moving at the rear wheels then Look at the wiring from the VSS to the ECM since you have already replaced the VSS sensor.

If you have a multimeter that has frequency, you could test the signal for the VSS at the PCM. PPL/WHT wire, pin 21 connector 2 and LT GRN/BLK wire, pin 21 connector 2. the voltage reading should be at least 0.5volts (and up as speed continues to rise) but you are looking for frequency, frequency should be around 4K pulses per mile.