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P1516 Fault Code on 2003 Chevrolet Silverado SS: Causes, Diagnosis & Solutions

Model: 03 Silverado SS Fault Code: P1516 Posted: 2006-05-28 13:51

I'm experiencing a recurring issue with my 2003 Chevrolet Silverado SS. The truck has accumulated 60,000 miles and has been modified with a Radix Magnacharger (2.9 pulley), ASM LT headers, air intake system, ram air hood, and a custom PCM tune from PCM4Less. I'm also using an Aeroforce Intercepter scan gauge to monitor engine performance. The problem began during a 1.5-hour drive when I experienced sudden 'ding...ding...ding' alerts indicating reduced engine power on the dashboard. After resetting via the scan gauge, I continued driving. Since then, the vehicle intermittently sets fault code P1516, which is associated with throttle body or TAC module issues. The symptoms occur primarily during moderate to full-throttle acceleration and are more frequent after the engine has warmed up. I've already checked all connections at the throttle body and TAC module, unhooked the battery, and reinstalled the PCM connectors multiple times. Despite these efforts, the issue persists. I'm wondering if there's any specific diagnostic insight I can gain from the Aeroforce Intercepter scan gauge. Could water ingress through the ram air hood be damaging internal throttle body components? Given that the problem worsens after heavy rain and appears more frequently when the engine is warm, this seems plausible. Is it possible for moisture to enter the throttle body via the throttle shaft? I'm considering replacing the throttle body and inspecting the old unit internally to identify any water damage or sensor failure. As a next step, I may need to have the issue data logged by a professional shop using a TECH2 or OTC scanner, as my current equipment lacks advanced diagnostic capabilities. Any advice on troubleshooting this P1516 code in a 2003 Silverado SS would be greatly appreciated.

Related fault codes
P1516
Comments (9)
Anonymous 2006-05-29 15:57

Have you inspected the throttle body for dirt or debris? A clogged or dirty throttle body can trigger P1516 and cause inconsistent engine power. Cleaning or replacement might resolve it.

Anonymous 2006-05-29 16:01

Check if any recent work was done in the engine bay—especially around ground straps. Ensure the harness leading to the TAC module isn't damaged, frayed, or rubbed through. Physical damage can cause intermittent faults like P1516.

Anonymous 2006-05-29 20:43

I recently installed a new PCM tune and replaced the original PCM. The issue started noticeably after heavy rain. My ram air hood may have allowed water ingress into the throttle body area. I suspect moisture could enter through the throttle shaft, especially as symptoms worsen when the engine is warm. I've observed three consecutive P1516 events today. The only code present is P1516, pointing to either the throttle body, TAC module, or wiring. I’ve reseated all connectors and saw no visible water—but may have missed something. My next step is to take it to a dealer or shop for data logging with a TECH2 or OTC scanner since my current reader lacks advanced diagnostics.

Anonymous 2006-05-30 08:47

If you have a functioning ram air hood that draws water, it's highly likely moisture is entering the throttle body. Check the wiring harness leading to the throttle body—especially about 6 inches back from the connection point—for signs of damage or corrosion. Also verify ground connections at the cylinder heads before replacing parts. Water ingress through the throttle shaft is a plausible cause. Good luck and stay updated!

Anonymous 2006-05-30 14:28

Thanks Jeff! I noticed the wiring to the throttle body appears twisted at the connection point. Are there any repair harnesses available for the throttle body end? I'm looking for a used one, but most junkyards keep them attached to engines. The mystery continues...

Anonymous 2006-05-30 15:56

If both ends of the connector appear intact, open up the harness and inspect all wires for damage or corrosion. As a temporary fix, consider running new wiring from the connector directly to the PCM or TAC module to isolate whether the issue lies in the harness. Unfortunately, many junkyards keep harnesses on engines because it simplifies engine swaps at shops—this can make troubleshooting difficult. I hope it's not the TAC module; they're expensive, and such components aren't widely available yet. Good luck and stay posted!

Anonymous 2006-05-30 22:13

I drove the truck tonight after a day of 90+ degree heat. It ran perfectly—no issues at all. This strongly suggests water was the root cause. I'm planning to replace the throttle body and inspect the old unit internally to identify any signs of moisture damage or internal component failure. If I can also resolve the P0748 code (after a shift kit installation), I’ll be fully satisfied with my truck’s performance. Thanks for all the help!

Anonymous 2006-05-31 11:33

Don't disassemble the throttle body until you've confirmed and resolved the root cause—avoid unnecessary damage or premature replacement.

Anonymous 2006-05-31 21:31

I drove approximately 60 miles today after replacing the throttle body. The P1516 code has disappeared, and no reduced engine power is present. I’ll eventually take apart the old throttle body to inspect internal components—especially the actuator motor and sensors—for signs of water intrusion or corrosion. Thanks again for all your input!