P2138 on 2016-2018 Chevrolet Spark: Reduced Power Causes and Fixes

What's Unique About the 2016-2018 Chevrolet SPARK

The Chevrolet Spark, like many other modern GM vehicles, is known for this specific issue. The problem is so prevalent that GM has issued multiple Technical Service Bulletins (TSBs) over the years. These bulletins, specifically TSB #07-06-04-019F, point not only to the accelerator pedal sensor itself but also to a specific wiring harness connector (often called the IP-to-Body harness connector) that is prone to water intrusion and corrosion. Water can leak from A-pillar seals or the windshield/cowl area and drip onto this connector, which is typically located in the driver's side kick panel. This corrosion disrupts the sensitive voltage signals from the pedal, causing the P2138 code even if the pedal itself is perfectly fine.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light illuminated
• "Reduced Engine Power" message displayed on the instrument cluster
• Poor or no acceleration
• Vehicle feels sluggish or won't accelerate past a certain speed (limp mode)
• Unstable or erratic idle
• Vehicle may buck or jerk on acceleration

Most Likely Causes

1. Faulty Accelerator Pedal Position (APP) Sensor 🔴 High Probability → Shop Accelerator Pedal Assembly The sensor is integrated into the accelerator pedal assembly, which is a common failure point on many GM vehicles of this era. Wear and tear on the internal contacts can cause the signals to become erratic.
   How to confirm: Using a scan tool with live data, monitor the voltage or percentage of APP Sensor 1 and APP Sensor 2 while pressing the pedal. The values should be different but change in a consistent, mirrored pattern. 🎬 See how to diagnose reduced engine power and sensor correlation issues. If one sensor is erratic, drops out, or doesn't respond smoothly, the assembly is faulty.
   Typical fix: Replace the entire accelerator pedal assembly. The sensors are not serviceable separately. The OEM part number for the 2016-2018 Spark is GM 95352200. 🎬 Watch: This easy DIY walkthrough shows how to replace the pedal.
   Est. part cost: $80-$150
2. Wiring or Connector Issue 🟡 Medium Probability GM TSB #07-06-04-019F specifically calls out water intrusion into the instrument panel-to-body harness connector as a cause for P2138 on many GM vehicles, including the Spark. This connector, sometimes designated X202 or similar, is often located in the driver's kick panel area and is vulnerable to leaks from the A-pillar or cowl. The resulting corrosion disrupts the sensor signals.
   How to confirm: Locate and inspect the IP-to-body harness connector (in the driver's side kick panel area) for any signs of moisture, green or white corrosion, or backed-out pins. Also inspect the connector directly at the accelerator pedal for damage or loose pins.
   Typical fix: Clean the corroded terminals using electrical contact cleaner and a small brush. If corrosion is severe, the connector pigtail may need to be replaced, or in extreme cases, the affected wires may need to be bypassed and run directly from the pedal to the ECM.
   Est. part cost: $20-$50 for a pigtail connector

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is very rare. All other possibilities, especially the APP sensor and wiring, should be exhaustively ruled out before considering PCM replacement.
• Dirty or Faulty Throttle Body: → Shop Fuel Injection Throttle Body While less common for this specific correlation code, a throttle body that is sticking or has a faulty internal Throttle Position Sensor (TPS) can sometimes cause related issues. However, this would typically set other codes like P2135, which points specifically to the throttle body sensors.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner to confirm P2138 is the primary code. Note any other APP-related codes (P2122, P2127, etc.).
2. Visually inspect the wiring and connector at the accelerator pedal for any obvious damage or loose connections.
3. Use a scan tool to view live data for 'APP Sensor 1' and 'APP Sensor 2'.
4. With the vehicle in 'key on, engine off', slowly press and release the accelerator pedal. Watch the live data streams. The two sensor readings should move smoothly and in correlation with each other (one may read about half of the other, or one may increase while the other decreases, but the movement should be consistent).
5. If you see glitches, spikes, or dropouts from one or both sensors in the live data, the accelerator pedal assembly is the most likely culprit.
6. If the pedal sensor data looks good, consult TSB #07-06-04-019F. Locate the instrument panel-to-body harness connector in the driver's side kick panel area. Disconnect the battery, then unplug the connector and inspect it thoroughly for signs of water damage or corrosion (blue/green powder).
7. If corrosion is found, clean the terminals with electrical contact cleaner and a nylon brush. Apply dielectric grease before reconnecting to prevent future moisture intrusion. Find and repair the source of the water leak (e.g., windshield seal, A-pillar trim, sunroof drain).
8. If no issues are found with the pedal or wiring, the problem could be a rare intermittent fault or an issue with the PCM, which may require professional diagnosis.

Parts You'll Likely Need

• Accelerator Pedal Assembly with Sensor (OEM #95352200) — This is the most common failure. The sensors are integrated into the pedal assembly and are not sold separately. Replacing the entire unit is the standard repair.
  Trusted brands: ACDelco, Dorman, GM Genuine Parts
  OEM price range: $120-$180
  Aftermarket price range: $80-$120

Related Codes That Often Appear With This One

• P2122: APP Sensor 1 Circuit Low Voltage
• P2123: APP Sensor 1 Circuit High Voltage
• P2127: APP Sensor 2 Circuit Low Voltage
• P2128: APP Sensor 2 Circuit High Voltage

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #07-06-04-019F: Intermittent Malfunction Indicator Lamp (MIL) Illuminated, DTC P2138 with Reduced Engine Power (Repair Instrument Panel (IP) to Body Harness Connector). This is the primary TSB for this issue across many GM models.

Platform-Specific Known Issues

• A known issue, documented in GM Technical Service Bulletin #07-06-04-019F, involves water intrusion into the instrument panel-to-body harness connector, leading to corrosion and causing a P2138 code. This connector is often found in the driver's side kick panel.
• While not a recall, GM has issued Special Coverage Adjustments for other models like the Malibu and LaCrosse for the exact same P2138 issue, extending the warranty on the pedal assembly to 10 years/150,000 miles. While the Spark is not officially included, it demonstrates GM's acknowledgement of the widespread nature of this part failure.

Mechanic-Grade Diagnostic Values

• APP Sensor 1 Signal Voltage — expected: Sweeps smoothly from ~0.5V to ~5.0V as pedal is pressed.. Failure: Voltage is erratic, jumps, or does not change with pedal movement.
• APP Sensor 2 Signal Voltage — expected: Sweeps smoothly from ~0V to ~2.5V; should be approximately half of APP Sensor 1's voltage.. Failure: Voltage does not correlate with Sensor 1, is erratic, or drops out.
• APP Sensor 5V Reference Voltage — expected: 4.8V to 5.2V at the APP sensor connector with key on, engine off.. Failure: Voltage is below 4.8V or absent, indicating an ECM or circuit issue.
• APP Sensor Low Reference (Ground) Circuit Resistance — expected: Less than 5 ohms between the low reference terminal at the APP connector and a good chassis ground.. Failure: Resistance is higher than 5 ohms, indicating a poor ground connection.
• Voltage Correlation between APP Sensor 1 and 2 — expected: The voltage difference should not exceed a predefined threshold (e.g., 0.5V) for more than a few seconds.. Failure: A divergence greater than 0.5V between the two sensor signals triggers the fault.

Hidden / Shadow Codes Worth Checking

• P2138:00: This is a more specific logging of the P2138 fault, but does not represent a separate 'shadow code'. It simply confirms the primary fault with a standard failure type code. (see via May be visible on some professional-grade scan tools like the Foxwell NT710.)

Scan Tool Commands That Help

• GDS2/Tech2 (or equivalent pro scanner): Throttle/Idle Learn Procedure — This function may be required after replacing the accelerator pedal assembly or the throttle body to allow the ECM to relearn the new component's position values.
• Manual Procedure (No Tool): Manual Throttle Relearn — If a scan tool is unavailable after part replacement or battery disconnect, a manual relearn can be attempted. A common GM procedure involves turning the ignition ON (engine off) for 3 minutes, OFF for 1 minute, starting the engine to idle for 3 minutes, then OFF for 1 minute, and repeating the idle cycle. Always verify the specific procedure for your vehicle.

Wiring & Ground Locations

• IP-to-Body Harness Connector (e.g., X101, X202) — Located in the driver's side kick panel area, near the floor. It is a large, multi-wire connector.. This is the specific connector cited in GM TSB #07-06-04-019F as being highly susceptible to water intrusion and corrosion, which directly disrupts the APP sensor signals traveling to the ECM.
• B107 (APP Sensor Connector) — The electrical connector at the accelerator pedal assembly itself.. This is the first point of connection. A 'wiggle test' here while monitoring live data can identify loose pins. A workshop manual for the M400 Spark identifies the 5V reference circuit at terminal 6 of this connector.
• K20 (Engine Control Module) — Located in the engine compartment.. This is the destination for the APP sensor signals. A workshop manual for the M400 Spark shows the 5V reference circuit for the APP sensor originates from pin 50 on the X1 connector of the ECM.

Real Owner Repair Stories

• YouTube channel 'Fix It All' (Chevrolet Sonic (uses a similar electronic throttle control system and is prone to the same code)) — Vehicle went into 'limp mode' with a P2138 code stored.
  ❌ Tried (didn't work) The user first checked wiring connections at the throttle body and pedal, which appeared normal.
  ✅ What actually fixed it Replacing the entire accelerator pedal assembly, which includes the integrated position sensor, resolved the code and limp mode condition.