P1516 on 2011-2015 GMC Savana: Throttle Control Performance Causes and Fixes

What's Unique About the 2011-2015 Gmc SAVANA

For high-mileage GMC Savanas and other GM V8 trucks of this era, P1516 is a very common code directly addressed by a Technical Service Bulletin (TSB). The TSB explains that over time, carbon builds up inside the throttle body, restricting the throttle plate's movement. The engine computer tries to compensate for this buildup by adjusting the idle throttle angle, but eventually, the restriction becomes too great, causing the position mismatch that sets code P1516. This makes a dirty throttle body the number one suspect, more so than on other platforms where wiring or sensor failure might be more common. Poor grounds are also a known secondary cause on this platform.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• "Reduced Engine Power" message on the dashboard
• Check Engine Light is on
• Vehicle has very limited acceleration (limp mode)
• Poor or no throttle response
• Idle surge or rough idle
• Engine may stall
• Engine turns over but will not start (in severe cases)

Most Likely Causes

1. Dirty or Carbon-Clogged Throttle Body 🔴 High Probability As documented in TSB #PIP4578B, carbon buildup is a known issue on high-mileage GM V8 engines, causing the throttle plate to stick or move slowly. The PCM learns to compensate for the buildup, which is why cleaning alone without a relearn is often not enough.
   How to confirm: Remove the air intake duct from the throttle body. Visually inspect the throttle plate and the inside of the throttle bore for a thick, black layer of carbon. The plate may feel sticky or slow to move when pushed lightly (with ignition off).
   Typical fix: Thoroughly clean the throttle body bore and plate with a dedicated throttle body cleaner and a soft brush/rag. 🎬 Watch: Step-by-step guide to cleaning your Savana's throttle body. An idle learn reset must be performed afterward to reset the PCM's learned values.
   Est. part cost: $5-$15
2. Failed Throttle Body Assembly 🟡 Medium Probability The internal electronics, such as the motor or the dual throttle position sensors (potentiometers), can wear out. The sensor's contact fingers can bend or wear down, creating dead spots that send faulty signals to the PCM.
   How to confirm: If a thorough cleaning, idle relearn, and wiring/ground check does not resolve the code, the throttle body assembly itself is the likely culprit. A scan tool can graph the TPS1 and TPS2 voltages to look for dropouts when the throttle is moved.
   Typical fix: Replace the entire throttle body assembly and perform an idle learn procedure.
   Est. part cost: $90-$250
3. Wiring or Connector Issue ⚪ Low Probability The 6-pin connector pigtail at the throttle body is a known failure point. Wires can break inside the insulation from vibration and heat, or the terminals can lose tension, causing intermittent connections. Wiggling the harness near the connector while the engine is running may trigger the fault.
   How to confirm: With the key off, unplug the throttle body connector. Inspect for corrosion, moisture, or backed-out pins. Gently tug on each of the six wires to ensure it is secure in the connector. Check for chafing on the harness loom.
   Typical fix: Repair the damaged section of wiring or replace the entire throttle body connector pigtail. Common pigtail part numbers include ACDelco PT2713.
   Est. part cost: $15-$40

Rare But Worth Checking

• Faulty or Loose Ground Connections: Several owners have fixed persistent P1516 issues by cleaning and tightening main engine and body grounds, or by adding redundant ground straps. Key ground locations to check on GM trucks 🎬 See how adding ground straps can fix persistent P1516 codes. are G103 and G104. A user on Tahoe Yukon Forum provided a detailed account of adding grounds from the firewall to the engine block to solve the problem after replacing parts failed to work.
• Powertrain Control Module (PCM) Issue: This is extremely rare. Before condemning the PCM, all other possibilities, especially the throttle body, its wiring, and all related ground connections, must be exhaustively ruled out.

Diagnosis Steps

1. Scan the vehicle for all stored DTCs. Note any other codes that appear with P1516, especially P2101, P0121, or P2135.
2. Inspect the wiring harness and 6-pin connector at the throttle body. Wiggle the harness with the engine running to see if it triggers the fault. Check for damaged wires or loose terminals.
3. Inspect engine ground straps. On GM trucks, grounds G103 and G104 are common culprits. Ensure they are clean, tight, and free of corrosion.
4. Remove the air intake hose from the throttle body.
5. Visually inspect the throttle bore and plate for heavy carbon buildup. This is the most likely cause.
6. If dirty, clean the throttle body thoroughly using a dedicated throttle body cleaner and a soft cloth. Do NOT spray cleaner directly into electrical components.
7. After cleaning, reassemble the intake and perform a 'Throttle/Idle Learn Reset'. This step is critical.
8. Manual Relearn Procedure (No Scan Tool): Start and idle the engine in Park for 3 minutes. The idle may be high. Turn the ignition OFF for 60 seconds. Start and idle the engine again in Park for another 3 minutes. The idle should now be normal. If not, a drive cycle above 44 MPH with several stops may be needed.
9. Clear the codes and test drive the vehicle. If the code returns, the throttle body assembly itself is likely faulty.
10. If the code persists after replacing the throttle body, re-inspect the wiring harness and grounds for intermittent faults before considering a PCM issue.

Parts You'll Likely Need

• Throttle Body Assembly (OEM #12601387, 217-3151) — If cleaning the original unit doesn't resolve the issue, the internal electronics or motor have likely failed, requiring a full replacement.
  Trusted brands: ACDelco, Standard Motor Products, Hitachi, Dorman
  OEM price range: $200-$280
  Aftermarket price range: $90-$170
• Throttle Body Cleaner — This is required for the most common fix: cleaning carbon buildup from the throttle plate and bore.
  Trusted brands: CRC, Berryman, Gumout
  OEM price range: $5-$15
  Aftermarket price range: $5-$15
• Throttle Body Connector Pigtail (OEM #ACDelco PT2713, 88988106) — The original connector can fail due to heat and vibration, causing a poor connection. Replacing the pigtail is a common repair for intermittent issues.
  Trusted brands: ACDelco, Dorman, Michigan Motorsports
  OEM price range: $25-$40
  Aftermarket price range: $15-$25
• Throttle Body Gasket (OEM #Fel-Pro 61469) — It is best practice to replace the gasket any time the throttle body is removed to prevent vacuum leaks.
  Trusted brands: Fel-Pro, Mahle, ACDelco
  OEM price range: $5-$15
  Aftermarket price range: $3-$10

Related Codes That Often Appear With This One

• P2101 — This code, 'Throttle Actuator Control Motor Circuit Range/Performance', is often set alongside P1516 as it also relates to the throttle body's motor performance. TSB #PIP4578B lists them together.
• P0121 — 'Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance' can appear because the PCM sees a conflict between different throttle position readings, often due to carbon buildup.
• P2135 — 'Throttle/Pedal Position Sensor/Switch 'A' / 'B' Voltage Correlation' indicates a disagreement between the two position sensors inside the throttle body, which can be a root cause or a related symptom.
• P0068 — 'MAP/MAF - Throttle Position Correlation' can be triggered when the airflow measured by the MAF sensor doesn't match what the PCM expects based on the reported throttle angle. TSB #PIP4578B also lists this code.

Technical Service Bulletins (TSBs) & Recalls

• PIP4578B: Addresses an idle surge, reduced engine power mode, and DTCs including P1516, P0068, P0121, P2101, P2119, and P2176 on high mileage vehicles due to carbon buildup in the throttle

Platform-Specific Known Issues

• GM Technical Service Bulletin PIP4578B directly addresses P1516 in conjunction with idle surge and reduced power mode on high-mileage vehicles, including the 2011-2015 Savana. The bulletin explicitly states that carbon buildup in the throttle body is the cause and that cleaning followed by an idle learn reset is the correct repair procedure.
• Poor ground connections are a well-documented secondary cause on this platform. A user on the Tahoe Yukon Forum detailed a successful repair by adding redundant ground wires after all other attempts failed, a story echoed by others.

Mechanic-Grade Diagnostic Values

• Throttle Position Sensor 1 (TPS1) Signal Voltage — expected: Approx. 0.8V to 1.2V at closed throttle, sweeping smoothly up to approx. 4.0V at wide-open throttle (WOT).. Failure: Voltage is outside the expected range, does not change with throttle movement, or shows sudden drops/spikes when graphed on a scan tool or oscilloscope.
• Throttle Position Sensor 2 (TPS2) Signal Voltage — expected: Approx. 2.3V to 3.1V at closed throttle, sweeping smoothly up to approx. 4.5V-5.0V at wide-open throttle (WOT).. Failure: Voltage is outside the expected range, does not change with throttle movement, or shows sudden drops/spikes. The two TPS signals should be clean and inversely correlated when graphed.
• 5-Volt Reference at Throttle Body Connector — expected: A steady 5.0 Volts at Pin E (Gray wire) with key-on, engine-off.. Failure: Voltage is significantly lower than 5.0V or is 0V. This can indicate a short in the harness or a problem with the PCM.

Scan Tool Commands That Help

• GM GDS2 / Tech2: Engine Control Module > Control Functions > Throttle Control — This function allows a technician to command the throttle plate to specific angles (e.g., 10%, 25%, 50%) and observe the actual reported position from the TPS sensors. It is used to verify if the throttle motor is responding correctly and if the sensors are reporting accurately after cleaning or when diagnosing a suspected faulty throttle body.

Wiring & Ground Locations

• G103 — On C/K trucks (including Savana), this ground is typically located on the front of the passenger side cylinder head.. A poor connection at G103 is a known cause for intermittent TAC module and throttle position codes. A GM service document specifically calls for checking the voltage drop on this ground when diagnosing P1516.
• G104 — Located on the rear of the driver's side cylinder head. A ground strap often runs from here to the firewall.. Like G103, this is a critical engine-to-chassis ground. Corrosion or looseness here can cause a variety of electrical issues, including the Reduced Engine Power mode associated with P1516.
• Throttle Body Connector — The 6-pin electrical connector on the throttle body assembly.. This is the single point of connection for the throttle motor, both TPS sensors, and their power/ground. Wires can break inside the insulation within 1-4 inches of the connector, causing intermittent faults that are hard to see visually.

Real Owner Repair Stories

• Tahoe Yukon Forum (2003+ GM Truck (similar platform)) — Recurring "Reduced Engine Power" message and code P1516, especially when hitting bumps.
  ❌ Tried (didn't work) Replacing the throttle body pigtail connector, Replacing the Throttle Position Sensor (TPS)
  ✅ What actually fixed it The owner resolved the issue by adding new, redundant ground wires. Specifically, a 10-gauge wire was added from the firewall to an unused threaded hole on the engine block (driver side valve cover), and a second ground wire was added from the TAC module to the firewall. This suggests the original factory grounds were insufficient or had developed high resistance.

When the Usual Fixes Don't Work

• While cleaning the throttle body or replacing the pigtail are the most common fixes, a significant number of owners have found that these steps do not resolve persistent, intermittent P1516 codes. In many of these cases, the ultimate root cause was found to be poor grounding. A detailed forum post describes a final, successful fix only after adding multiple new ground straps between the engine, firewall, and key components, even after factory grounds appeared visually intact. This highlights that for stubborn cases, focusing on improving the ground system can be more effective than replacing more parts.

OEM Part Supersession History

• 12601387 → 12629992 — Standard part revision and consolidation by GM.
  Heads up: The new part number 12629992 is a direct replacement for 12601387. However, some documentation notes that the replacement part may require programming or special setup procedures, which can be performed with dealer-level tools like GDS2.