P1682 on 2007-2014 GMC Acadia: Ignition Circuit Fault, Stalling, and Fixes

What's Unique About the 2007-2014 Gmc ACADIA

The first-generation GMC Acadia and its GM Lambda platform siblings (Buick Enclave, Chevrolet Traverse, Saturn Outlook) are known for issues with the Underhood Bussed Electrical Center (UBEC), or fuse box. The design can be susceptible to moisture intrusion and vibration, leading to corrosion and poor terminal tension. This specific issue is so common that GM has issued multiple Technical Service Bulletins (TSBs) pointing directly to a corroded or burnt terminal pin in a specific connector (X3, pin 51) of the UBEC as the primary cause for P1682.

Diagnostic Flowchart

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

Symptoms You May Notice

• Engine stalls intermittently, sometimes while driving, especially when coming to a stop.
• "Reduced Engine Power" message displayed on the dash.
• Check Engine Light (Service Engine Soon MIL) is on.
• Engine cranks but does not start (no-start condition).
• Vehicle jerks or loses acceleration suddenly. [ODI #11699625]
• Dead battery or noticeable battery drain overnight. [Bulletin #PIT4649B]
• Multiple warning lights (ABS, Traction Control) may appear simultaneously with the stall.
🎬 See how a fuse box replacement fixes stalling and ABS lights.
• Engine continues to run even after the key is turned off and removed.

Most Likely Causes

1. Corroded or Loose Terminal in Underhood Fuse Box (UBEC) 🔴 High Probability → Shop Fuse Box This is a well-documented issue on the GM Lambda platform. TSBs #PIT5643 and #19-NA-276 specifically call out poor terminal tension and arcing/corrosion on terminal 51 of the X3 connector in the UBEC. The damage often appears as a small, dark burn mark or discoloration on the male pin of the fuse box and the female terminal in the connector.
   How to confirm: Disconnect the battery. Remove the UBEC and turn it over to inspect the connectors on the bottom. Carefully examine terminal 51 of the X3 connector for any signs of green or white corrosion, black sooty marks from arcing, melted plastic, or a loose-fitting pin. Using a phone camera to zoom in can help identify the subtle burn marks.
   Typical fix: If the damage is minimal, the single wire terminal (terminated lead) can be replaced. If the fuse box itself is burnt or corroded at the pin, the entire UBEC assembly must be replaced along with the terminal.
   Est. part cost: $15-$40 for a terminated lead, $250-$450 for a new UBEC.
2. Faulty Powertrain or Run/Crank Relay 🟡 Medium Probability → Shop Wiring Relay These relays control the power circuits that the ECM monitors. Over time, their internal contacts can wear out or fail, causing an intermittent connection. While less common than the terminal issue, it's a simple and inexpensive diagnostic step.
   How to confirm: Locate the Powertrain (PWR/TRN) and Run/Crank (RUN/CRK) relays in the UBEC. Swap them with identical, known-good relays from non-critical systems (like the horn or rear defogger). If the problem disappears or changes, the relay is faulty.
   Typical fix: Replace the faulty relay.
   Est. part cost: $15-$40
3. Faulty Ignition Switch ⚪ Low Probability → Shop Ignition Switch While less common than the UBEC issue for this specific code on this platform, a failing ignition switch can cause erratic voltage on ignition circuits. Symptoms can sometimes include the engine failing to shut off when the key is removed.
   How to confirm: This requires testing the voltage outputs from the ignition switch in various key positions using a multimeter and a wiring diagram. If voltage is intermittent or incorrect on the circuits feeding the ECM relays, the switch is likely bad.
   Typical fix: Replace the ignition switch.
   Est. part cost: $30-$70

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is very rare. Before condemning the ECM, all other possibilities, especially the UBEC and its wiring, must be exhaustively checked. An ECM failure might be accompanied by other communication codes.
• Internal UBEC Trace Failure: In some cases, the internal copper traces within the multi-layered fuse box itself can crack or break, causing an open circuit. This is not visually obvious from the outside and requires either replacing the UBEC or attempting a complex internal repair by splitting the fuse box housing.

Diagnosis Steps

1. Scan for all diagnostic trouble codes. If P0689 is present, diagnose it alongside P1682 🎬 Watch: Real-world diagnosis of an Acadia with P0689 and P1682. as they share a common cause.
2. Check for any active Technical Service Bulletins (TSBs) for your vehicle's VIN related to P1682. TSBs #19-NA-276 and #PIT5643 are highly relevant.
3. Perform a simple relay swap. Locate the RUN/CRK and PWR/TRN relays in the underhood fuse box and swap them with identical relays for other systems (e.g., horn). Clear codes and see if the issue is resolved.
4. If the engine runs, try wiggling the wiring harnesses connected to the UBEC to see if the stall or fault can be induced, which would confirm a loose connection.
5. Disconnect the negative battery terminal.
6. Remove the underhood fuse box (UBEC) to access the large connectors on the underside. This involves removing several nuts and releasing multiple retaining tabs.
7. Thoroughly inspect terminal 51 of the X3 connector for any signs of corrosion, heat damage, or arcing (black marks). Also check the corresponding male pin on the UBEC itself for damage. The damage can be a very subtle dark spot.
8. Check the tension of the female terminal. It should grip a test probe tightly. If it feels loose compared to its neighbors, it has failed, even if no corrosion is visible.
9. If corrosion or damage is found, replace the affected terminal lead and/or the entire UBEC assembly as needed.
10. If no issues are found at the UBEC, proceed to test the ignition switch and the wiring between the switch, UBEC, and ECM for continuity and proper voltage.

Parts You'll Likely Need

• Underhood Bussed Electrical Center (UBEC) (OEM #22921521, 20857798 (numbers may vary by year/options, verify with VIN)) — This is the most common point of failure. Corrosion or internal breaks cause the voltage discrepancy that sets P1682. Often, the damage to the pin on the box necessitates replacing the whole unit.
  Trusted brands: ACDelco (OEM)
  OEM price range: $300-$450
  Aftermarket price range: $250-$400
• Terminated Lead (UBEC Connector Wire) (OEM #84757974 (replaces 19301751, 19301767)) — If the fuse box pin is okay but the female terminal in the connector is corroded or has lost tension, this single wire with a pre-crimped terminal is used for the repair.
  Trusted brands: ACDelco (OEM)
  OEM price range: $15-$40
• Powertrain or Run/Crank Relay — A failing relay can cause an intermittent open in the ECM's power circuit, triggering the code. It's a common and inexpensive part to rule out.
  Trusted brands: ACDelco, Bosch, Standard Motor Products
  OEM price range: $25-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0689 — P0689 (ECM/PCM Power Relay Sense Circuit Low) is frequently stored with P1682 because both codes relate to the ECM's power supply and monitoring circuits. The same fault, like a bad terminal in the fuse box, can trigger both codes.

Technical Service Bulletins (TSBs) & Recalls

• 19-NA-276: 'Potential Reduced Engine Power Message Displayed and/or Engine Stall with DTCs P1682 and/or P0689 Set.' Points to poor terminal tension on terminal 51 in the underhood fuse block.
• PIT5643: 'Intermittent Reduced Engine Power or Stall with P0689 and/or P1682.' Cites arcing/corrosion on terminal 51 of the X3 connector at the UBEC.
• PIT4649B: 'Service Engine Soon MIL With

Platform-Specific Known Issues

• A known issue, documented in GM TSB #19-NA-276, points to poor terminal tension at pin 51 of the X3 connector on the underhood fuse block, causing stalling and reduced power with codes P1682 and P0689.
• GM Preliminary Information bulletin #PIT5643 also highlights the potential for arcing and corrosion on terminal 51 of the X3 connector at the UBEC as the cause for these codes.
• Owner Repair Experience: In a detailed video, an owner of a 2014 Acadia with P1682 and P0689 documented the entire repair. After experiencing severe stalling, he inspected the UBEC and found a very small, dark arc mark on pin 51. Replacing the entire fuse box and the corresponding wire terminal completely resolved the stalling issue. This highlights how minor the visible damage can be, yet still cause major problems.

Mechanic-Grade Diagnostic Values

• Voltage difference between 'Ignition 1 Voltage' and 'EC Ignition Relay Feedback' on a scan tool — expected: Less than 3 volts. Failure: A voltage difference greater than 3 volts for more than a second will set the DTC.
• Voltage at ECM Connector C1, Pin 19 (Ignition 1 Voltage from Run/Crank Relay) — expected: Battery Positive Voltage (B+). Failure: Voltage significantly less than B+ indicates an open or high resistance in the circuit from the UBEC.
• Resistance in the ignition 1 voltage circuit from the UBEC fuse to the ECM — expected: Less than 5.0 ohms. Failure: A resistance of 5.0 ohms or greater can cause the DTC to set.

Scan Tool Commands That Help

• GDS2 / Tech2: Observe 'Ignition 1 Voltage' and 'EC Ignition Relay Feedback' parameters. — This is the primary diagnostic data to monitor when diagnosing P1682. It directly shows the two voltage inputs the ECM is comparing. A discrepancy between these values confirms the fault condition.

Wiring & Ground Locations

• X3 Connector — On the underside of the Underhood Bussed Electrical Center (UBEC) / fuse box, located on the passenger side of the engine compartment.. Pin 51 of this connector is the most common failure point, where corrosion or poor tension causes the voltage drop that triggers P1682.
• G103 — On the left side of the engine compartment, on the left inner fender panel (for 2013+ models) or on the cowl above the brake booster (earlier models).. This is a major ground point for the Body Control Module (BCM), Instrument Panel Cluster (IPC), and Data Link Connector (DLC). A poor ground here can cause widespread, erratic electrical issues that could mimic an ignition circuit fault.
• G112 / G114 — At the rear of the engine, mounted to the rear of the cylinder head.. These are engine block grounds. While not directly tied to the ignition switch circuits, a poor engine ground can cause voltage potential differences and electrical noise that may affect ECM readings.
• G115 — On the left side of the engine compartment, on the left inner fender panel.. This ground is used by the Electronic Brake Control Module (EBCM). While not a primary cause, a fault here can contribute to multiple warning lights appearing along with the P1682 code.

Real Owner Repair Stories

• YouTube channel 'Sparky's Answers' (2014 GMC Acadia) — Engine would stall intermittently. Codes P0689 and P1682 were stored.
  ❌ Tried (didn't work) The owner had the vehicle brought to a shop, but the video starts with the diagnosis pointing towards the TSBs related to the UBEC.
  ✅ What actually fixed it The technician inspected the underside of the UBEC and found a dull, darker, discolored terminal at pin 51 of the X3 connector, indicating arcing. The fix involved replacing the entire UBEC and the single terminated wire lead for pin 51. This resolved the stalling.
• YouTube channel 'C&J's Mobile Automotive LLC' (2007 GMC Envoy (similar platform/issue)) — Vehicle would stall when warm and then fail to restart. Codes P1682 and P0689 were present.
  ❌ Tried (didn't work) Initial checks of power coming out of the fuse box were weak.
  ✅ What actually fixed it The technician disassembled the entire UBEC by drilling out the plastic rivets. An internal copper trace was found to be cracked. The trace was soldered back together, restoring continuity and fixing the no-start/stalling condition.

OEM Part Supersession History

• 19301751, 19301767 → 84757974 — Standard part consolidation and potential minor improvements to the terminal design or wire gauge.

Model Year Variations Within This Range

• 2007-2012 vs 2013-2014: The vehicle received a facelift in 2013. While the core P1682 issue related to the UBEC persists across the generation, specific ground point locations (like G103) and some fuse box layouts may have minor differences. Always verify wiring diagrams specific to the vehicle year.