Samthe man

I have a 2003 Silverado LS 4.8 230,000 miles. About 10 months ago I experienced the REDUCED ENGINE POWER reading. I cut truck off and restarted and had not seen the reading again until 5 days ago. I pulled the trouble code P1516 So I cleaned the throttle body and the MAF sensor. Truck ran fine for about 50 miles and than on my way home last night my truck keep stalling and did not show REDUCED ENGINE POWER. Took a scan the next morning and pulled 2 fault codes P0171 & P0174. went back and check for air intake leaks checked MAF connection to air filter housing and air tunnel connection to TB. Scanned again and pulled the P1516 fault code again without the P0171 & P0174 codes. Now my truck will only turn over and not crank. Do any one know if not cranking is a symptom of a defective throttle body or even an O2 sensor?

Thanks,

fursty

DTC P1516
Circuit Description
The predicted throttle position (TP) is compared to the actual throttle position. The two values should be within a calibrated range of each other. Both the powertrain control module (PCM) and the throttle actuator control (TAC) module redundantly monitor the predicted and actual throttle position. This DTC sets if the PCM detects an out of range condition between the predicted and actual throttle position.

Conditions for Running the DTC
•DTC P1518 is not set.
•The ignition switch is in the crank or run position.
•The ignition voltage is more than 5.23 volts.
•The TAC system is not in the battery saver mode.
Conditions for Setting the DTC
•The TAC module detects that the predicted and the actual throttle positions are not within a calibrated range of each other.
•The PCM and the TAC cannot determine the throttle position.
•Both of the TP sensors are invalid.
•All of the above conditions are met for more than 1 second.
Action Taken When the DTC Sets
•The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
•The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
•The control module commands the TAC system to operate in the Reduced Engine Power mode.
•A message center or an indicator displays Reduced Engine Power.
•Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
•The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
•A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
•A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
•Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
•Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
•Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
•When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
(from GM service)

Not sure why it is not cranking, but those sensors should not put it in a no crank mode.

Samthe man

Thanks Fursty, I did another scan today after fully charging the battery and still had the P1516 code but this time the P0171 &P0174 codes did not come up but PO220 Throttle/Pedal Position Sensor/Switch B Circuit & P0120 A Circuit with the P1516 TAC codes came out. Checked all wires in TB harness all was good, went to check the ground wires that is connect behind the manifold intake, I found the ground strap on the driver side fire wall but black wire that runs on the passenger side was not there. Trying to cover all bases before I start replacing parts. Truck still will not crank.

Samthe man

The system is not throwing any more codes today (p1516) (PO120) (P0220) but truck will still crank when cold and run only if I depress the pedal and than stall after a few minutes. I cleaned the MAF and checked for air leaks. But yesterday the P1516 code was thrown. Its weird how one day I get DTC'S the next day I don't. I have already ordered the Throttle Body Assembly because I think the the actulator is bad checked the wires at the harness, paving big problems getting to the ground that's connected to the rear of the manifold intake. any advice out there today? Need truck back running

stone123

Hey, I’ve been running into problems with my truck. It’s a 2003 Silverado with a 5.3 and it keeps giving me a “reduced engine power” message and a p1516 code. Online it says that it’s the throttle actuator control module and I replaced that with a new one and it didn’t fix the problem. I’ve also replaced the throttle body with the sensor, the pedal sensor, and the o2 sensors. I added the extra ground wires along with cleaning the existing ones. I’ve checked the harness around the throttle body and the wires appear to be in good shape and no burnt ends on any connections and it still has the problem intermittently. I clear the codes while driving the truck and it continues driving normally with no problems. Do you have any idea what might cause it to do this?