truck won't start

waterdog · 12-29-2005, 06:25 PM

I need some help here. I have a 96 Silverado. It will turn over fine but won't fire. I've checked plugs, definately have spark, tested ignition module, changed coil. I replaced the fuel pump 2 years ago. Can hear it when I turn the key on. Replaced the distributor cap and rotor recently. Motor is a 305 5.0 Vortec. Fuel filter seems ok. Checked fuel pressure. Has 65 psi but drops to 0 as soon as you turn the key off. Getting OBDII codes P0122 and P0102. Anyone know if this could be the reason it won't start? The P0122 is TBS circuit low input and the P0102 is MAF circuit low input.
Found this online but I don't know anything about it:

A faulty TPS could result in a no start, start and stall, erratic performance or transmition shifting problem depending on the type of faulty. Generally a faulty TPS will see the following codes:
OBDI codes
21 Throttle Position (TP) sensor circuit (signal voltage high)
22 Throttle Position (TP) sensor circuit (signal voltage low)

OBDII codes
P0121 Throttle Position (TP) sensor circuit insufficient signal activity
P0122 Throttle Position (TP) sensor circuit low voltage
P0123 Throttle Position (TP) sensor circuit high voltage

Anyone know anything about throttle position sensor?
thanks

gmtech · 12-30-2005, 11:10 PM

Try the basics have someone spray a little carb cleaner into the tbi while turning it over and see if it starts or atleast tries then atleast you know its a fuel concern. The presuure should not drop it should hold and if it is dropping it could be a fuel pressure regulator leaking or a cracked injector housing.

12-29-2005, 06:25 PM	#1
waterdog Junior Member Join Date: Dec 2005 Posts: 1	truck won't start I need some help here. I have a 96 Silverado. It will turn over fine but won't fire. I've checked plugs, definately have spark, tested ignition module, changed coil. I replaced the fuel pump 2 years ago. Can hear it when I turn the key on. Replaced the distributor cap and rotor recently. Motor is a 305 5.0 Vortec. Fuel filter seems ok. Checked fuel pressure. Has 65 psi but drops to 0 as soon as you turn the key off. Getting OBDII codes P0122 and P0102. Anyone know if this could be the reason it won't start? The P0122 is TBS circuit low input and the P0102 is MAF circuit low input. Found this online but I don't know anything about it: A faulty TPS could result in a no start, start and stall, erratic performance or transmition shifting problem depending on the type of faulty. Generally a faulty TPS will see the following codes: OBDI codes 21 Throttle Position (TP) sensor circuit (signal voltage high) 22 Throttle Position (TP) sensor circuit (signal voltage low) OBDII codes P0121 Throttle Position (TP) sensor circuit insufficient signal activity P0122 Throttle Position (TP) sensor circuit low voltage P0123 Throttle Position (TP) sensor circuit high voltage Anyone know anything about throttle position sensor? thanks

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12-30-2005, 11:10 PM	#2
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 348	Try the basics have someone spray a little carb cleaner into the tbi while turning it over and see if it starts or atleast tries then atleast you know its a fuel concern. The presuure should not drop it should hold and if it is dropping it could be a fuel pressure regulator leaking or a cracked injector housing.