P0351 on 2005-2015 Toyota Tacoma 4.0L V6: Ignition Coil 'A' Circuit Causes and Fixes

What's Unique About the 2005-2015 Toyota Tacoma

The 1GR-FE engine in the second-generation Tacoma uses a very reliable coil-on-plug ignition system, but the coils are a common wear item after 100,000 miles. The P035x series of codes are straightforward on this platform; the computer is very good at isolating the specific failing coil circuit. Unlike some other vehicles where this code can be ambiguous, on the Tacoma, it almost always points directly to the coil itself or its immediate wiring, making diagnosis relatively simple for DIYers.

Symptoms You May Notice

• Check Engine Light is on (may be flashing if the misfire is severe)
• Rough or shaky idle
• Engine hesitation or stumbling during acceleration
• Noticeable loss of engine power
• Reduced fuel economy
• In rare cases, especially with wiring issues, the engine may stall or fail to start.
🎬 Watch: How a P0351 code caused a no-start condition

Most Likely Causes

1. Failed Ignition Coil on Cylinder #1 🔴 High Probability → Shop Ignition Coil Ignition coils are a maintenance part that wear out over time due to high voltage and constant heat cycles in the engine bay. It's the most common failure point for this code, often after 100,000 miles.
   How to confirm: Swap the ignition coil from cylinder #1 with the coil from cylinder #3 (the next one back on the passenger side). Clear the codes and drive. If the code changes to P0353, the coil is bad. Cylinder #1 is the front-most cylinder on the passenger side.
   Typical fix: Replace the faulty ignition coil. It is held in by a single 10mm bolt.
   Est. part cost: $45-$90
2. Damaged Wiring or Connector 🟡 Medium Probability Engine bay heat can make the plastic connector and wire insulation brittle over time. Rodents are also known to chew on the soy-based wiring insulation. A specific, documented failure is corrosion in butt connectors used for aftermarket accessories like remote starters, if they tap into the ignition signal wires.
   How to confirm: After confirming the coil is not the issue, visually inspect the wiring harness and connector for cylinder #1. Look for cracks, chafing, corrosion on the pins, or signs of rodent damage. Wiggle the connector with the engine running to see if it affects the idle. Check any aftermarket wiring tapped into the ignition system.
   Typical fix: Repair the broken/chewed wire or replace the pigtail connector if the lock is broken or pins are corroded. Remove and properly solder any corroded aftermarket connectors.
   Est. part cost: $10-$25 for a new pigtail connector
3. Worn or Fouled Spark Plug ⚪ Low Probability → Shop Spark Plug While P0351 is an electrical circuit code, a severely worn or oil-fouled spark plug can sometimes cause issues that stress the coil, leading to its eventual failure. It's often replaced at the same time as the coil as good practice.
   How to confirm: Remove the spark plug from cylinder #1 and inspect its condition. Look for a worn electrode, heavy carbon buildup, or oil fouling.
   Typical fix: Replace the spark plug. If replacing one, it's best practice to replace all six if they are near the end of their service life. 🎬 See this step-by-step spark plug replacement walkthrough
   Est. part cost: $8-$15 per plug

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) This is very rare. The internal driver circuit for the coil can fail. This should only be considered after definitively ruling out the coil, wiring, and spark plug.

Diagnosis Steps

1. Identify Cylinder #1: Locate cylinder #1 on your 1GR-FE engine. It is the cylinder at the front of the engine (closest to the radiator) on the passenger side.
2. Perform the 'Coil Swap' Test: Turn off the engine. Disconnect the electrical connector and remove the 10mm bolt holding the ignition coil for cylinder #1. Remove the coil. Do the same for cylinder #3 (the next coil back on the same side). Swap their positions: install the coil from #1 onto cylinder #3, and the coil from #3 onto cylinder #1. Reinstall bolts and connectors.
3. Clear Codes and Test Drive: Use an OBD-II scanner to clear the trouble codes. Drive the vehicle for 5-10 minutes.
4. Re-Scan for Codes: If the code P0353 appears, it confirms the ignition coil you moved is faulty. Purchase and install a new coil.
5. Inspect Wiring: If the original P0351 code returns, the problem is not the coil. The issue lies in the wiring or connector for cylinder #1. Carefully inspect the harness for any visible damage, corrosion, or loose connections. Pay special attention to any aftermarket wiring (like for a remote start) that may be tapped into the ignition harness.
6. Inspect Spark Plug: If the wiring appears perfect, remove and inspect the spark plug for cylinder #1 to ensure it is in good condition.
7. Check Grounds: Some owners have reported that cleaning engine and body ground points can resolve intermittent electrical issues that may contribute to the code.
8. Suspect ECM: If all other steps fail to find the issue, the problem may be a rare failure of the ECM's internal driver. This step often requires professional diagnosis.

Parts You'll Likely Need

• Ignition Coil (OEM #90919-02248, superseded by 90919-A2001, 90919-A2006, 90919-02260) — This is the most common cause of a P0351 code. The original part number was 90919-02248, which has been replaced by several updated versions.
  Trusted brands: Denso (OEM Supplier), NGK
  OEM price range: $70-$100
  Aftermarket price range: $45-$75
• Spark Plug (OEM #90919-01233) — It is good practice to replace the spark plug when replacing a coil, especially if its service interval is approaching.
  Trusted brands: Denso, NGK
  OEM price range: $12-$20
  Aftermarket price range: $8-$15
• Ignition Coil Connector Pigtail — Needed if the original connector's locking tab is broken or the terminals are corroded and cannot be cleaned.
  Trusted brands: Dorman, Standard Motor Products
  OEM price range: $20-$35
  Aftermarket price range: $10-$25

Related Codes That Often Appear With This One

• P0301 — P0301 means 'Cylinder 1 Misfire Detected'. Since P0351 indicates a fault in the ignition circuit for cylinder 1, it directly causes a misfire in that same cylinder.

Technical Service Bulletins (TSBs) & Recalls

• No specific Technical Service Bulletins (TSBs) have been issued by Toyota for the P0351 code on this platform. The diagnostic procedure is considered straightforward. However, numerous TSBs and warranty programs exist for other common 1GR-FE engine and Tacoma platform issues.

Platform-Specific Known Issues

• Rodent Damage to Wiring: The soy-based wiring insulation used in this generation of Tacoma can attract rodents, who may chew through the ignition coil wires, causing an open or short circuit that triggers P0351. This is a well-documented complaint among owners.

Mechanic-Grade Diagnostic Values

• Ignition Coil Driver Signal (IGT) — expected: 5 to 20 Hz. Failure: A reading of 0 Hz indicates no trigger signal from the ECM. A steady DC voltage indicates a short in the circuit.
• Ignition Coil Power Supply — expected: Battery Positive Voltage (approx. 12V). Failure: Low or no voltage indicates a problem with the power supply wire or ignition relay.
• IGT and IGF Signal Waveform — expected: A clean square wave for both signals.. Failure: A missing, noisy, or distorted waveform indicates a fault in the wiring, coil igniter, or ECM.

Hidden / Shadow Codes Worth Checking

• Freeze Frame Data: While not a hidden code, professional scan tools like Toyota's Techstream can access Freeze Frame Data. This is a snapshot of all major sensor values (engine speed, coolant temp, vehicle speed, etc.) at the exact moment the P0351 code was triggered. It is invaluable for diagnosing intermittent faults by revealing the conditions under which the fault occurs. (see via Toyota Techstream software or other advanced, professional-grade OBD-II scanners.)

Scan Tool Commands That Help

• Toyota Techstream: Active Test: Control the Spark — This bidirectional function allows a technician to command a spark event on a single, specific cylinder with the engine off. If the spark plug fires during the test, it confirms the ECM driver, wiring harness, and ignition coil for that cylinder are all functional, pointing towards an intermittent issue or a problem that only occurs under running conditions.

Wiring & Ground Locations

• Ignition Coil Connector (Cylinder 1) — On top of the ignition coil for the front-most cylinder on the passenger side of the engine.. This is the primary connection point to test for power, ground, and the IGT/IGF signals. The 4 pins are typically: Pin 1 (+B - Power), Pin 2 (IGT - Trigger), Pin 3 (IGF - Confirmation), Pin 4 (GND - Ground).
• EA, EB — These are key ground points located on the 1GR-FE engine block itself, typically on the cylinder heads or front of the engine. Specific locations are detailed in the factory service manual wiring diagrams.. A poor engine ground can cause a host of intermittent electrical issues, including ignition faults. The ignition coils rely on a solid ground connection (via Pin 4 and the engine block) to function correctly. Cleaning these main ground points is a valid troubleshooting step for persistent, hard-to-diagnose electrical codes.
• ECM Terminals (IGT1, IGF1) — Located at the main Engine Control Module (ECM) connectors, typically behind the glove box.. These are the specific pins on the ECM that send the trigger signal (IGT1) to and receive the confirmation signal (IGF1) from the cylinder 1 ignition coil. Testing for continuity between these pins and the coil connector pins can definitively rule out a wiring break.

Real Owner Repair Stories

• YouTube video '03 Toyota Tacoma. code P0351. Cut off and Wouldn't start! problem Solved!' (2003 Toyota Tacoma SR5) — Engine would cut off, sometimes fail to start, run rough, and then sometimes run perfectly. Tachometer needle would bounce erratically.
  ❌ Tried (didn't work) Initial thought was to replace the ignition coil, but the intermittent stalling pointed away from a simple coil failure.
  ✅ What actually fixed it Found a corroded butt connector on a wire for an aftermarket remote start system that was tapped into the factory tachometer/igniter signal wire. The corroded connector created an intermittent open circuit. The fix was to remove the butt connector and properly solder the wires.
• TacomaWorld Forum Thread 'Intermittant P0351 but no performance issues' (2003 Toyota Tacoma TRD Supercharged) — Intermittent P0351 code only on startup, with no noticeable misfire or performance problems. The owner discovered they could replicate the code by leaving the ignition key in the 'ON' position for a few seconds before cranking the engine.
  ❌ Tried (didn't work) Replacing the ignition coil for cylinder 1., Replacing the spark plugs.
  ✅ What actually fixed it The thread ends without a definitive final fix from the original poster, but another user with the exact same symptoms suspected a voltage issue during startup and mentioned fixing numerous wiring problems under the dash left by a previous owner. The key takeaway for diagnosis is the unique symptom of the code being triggered by a key-on delay before starting.
• NHTSA ODI #10969044 — While reported on a different model of the same manufacturer, an owner noted that after a loss of power and the replacement of all six coils, a P0351 code (bad coil on cylinder 1) was thrown only nine months and 7,000 miles later, followed shortly by a P0355 code.

"I Checked Everything" — The Actual Cause

• The diagnostic equivalent for this electrical code is 'coil and plug swap shows no fault'. A well-documented case involved a P0351 with stalling where the coil and plug were not at fault. The root cause was a corroded butt connector from an aftermarket remote start system that was poorly spliced into the igniter signal wire, causing an intermittent open circuit. Standard component checks would miss this entirely.

When the Usual Fixes Don't Work

• In cases where the P0351 code returns intermittently even after replacing the coil and spark plug, the root cause is often not a defective part but an underlying wiring issue. One owner on a forum was able to resolve a persistent, intermittent P0351 by methodically cleaning all major engine and body ground connection points. Another real-world case that stumped standard diagnosis was traced to a corroded wire splice from a poorly installed aftermarket remote starter, which only caused issues intermittently. These cases highlight that if the simple coil swap test doesn't provide a definitive answer, the next step should be a thorough inspection of the wiring harness, connectors, and grounds, especially if any aftermarket accessories are installed.

OEM Part Supersession History

• 90919-02248 → 90919-02260, 90919-A2001, 90919-A2006 — Standard part revision and supplier updates over the vehicle's production life.
  Heads up: While multiple part numbers will fit, forum consensus strongly advises using only coils made by the OEM supplier, Denso, to avoid premature failure or intermittent issues that can be caused by off-brand aftermarket coils.

Model Year Variations Within This Range

• 2005-2009 vs 2010-2015: Starting in model year 2010, the 1GR-FE engine was updated with Dual VVT-i (variable valve timing on both intake and exhaust cams). The earlier 2005-2009 models used single VVT-i (intake only). The updated engine also featured redesigned cylinder heads, roller rocker arms, and a higher compression ratio. While the fundamental P0351 diagnostic process remains the same, the ECM part numbers and potentially some engine harness wiring may differ between these two versions.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Frame Rust Perforation 🔴 High — Very common, especially in cold climate states with high road salt usage. Affects both 1st and 2nd generation Tacomas. (Ref: Multiple Warranty Enhancement Programs (e.g., ZH6, ZKA) and Limited Service Campaigns (e.g., K0D) were issued, not a formal recall. These programs offered frame inspection and, if perforation was found, frame replacement or vehicle buyback depending on the program terms.)
• Secondary Air Injection System Failure 🟠 Medium — Common, particularly noted on 2012 models. Caused by moisture entering the air pump, leading to pump and/or valve failure. Throws codes P2440, P2442, P2445. (Ref: Yes, T-SB-0033-17 Rev1 and T-SB-0333-17 address this issue, outlining the replacement of the pump, valves, and addition of a protective cover.)
• Head Gasket Failure (Early Models) 🔴 High — A noted weakness primarily on 2005 and some early 2006 models. The failure often occurs between 100,000 and 150,000 miles. (Ref: No TSB or recall, but it is a widely discussed issue in owner communities. Toyota reportedly updated the head gasket design in later 2006 models.)
• Rear Leaf Spring Fracture 🔴 High — Sufficiently common on 2005-2011 models that it prompted a recall. Springs could corrode and break. (Ref: Yes, a recall was issued where leaf springs could fracture, potentially contacting the fuel tank.)
• Clear Coat / Paint Peeling 🟡 Low — Cosmetic issue reported on various 2nd generation models, where the clear coat and sometimes paint layer can delaminate and peel. (Ref: No TSB or recall, but a common owner complaint.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, a used OEM Denso ignition coil from a documented low-mileage (under 100k miles) wrecked vehicle can be a cost-effective alternative to a new part. A used wiring connector pigtail is also a perfectly acceptable repair part.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Check the plastic body of the coil for any cracks or signs of heat damage.
• Inspect the electrical connector pins for any corrosion or damage.
• Ensure the rubber boot that seals against the spark plug tube is soft, pliable, and free of tears.

OEM-only on this vehicle (don't cheap out):

• Ignition Coil

Aftermarket brands forum-validated for this vehicle:

• Denso (OEM supplier)
• NGK (Generally considered a high-quality alternative, though Denso is the original equipment)

Brands owners have reported issues with on this vehicle:

• Generic, unbranded multi-packs sold on Amazon or eBay.
• Store brands (e.g., O'Reilly's) have been reported by some owners to fail prematurely.
• Bosch coils have been reported by owners to have a short lifespan in Toyota engines.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0353 — The code that appears if a faulty ignition coil from cylinder #1 is moved to cylinder #3 during diagnostic testing.
• P2440 — Related to Secondary Air Injection System failure, a common platform issue noted alongside ignition concerns on certain model years.
• P2442 — Related to Secondary Air Injection System failure, often caused by moisture entering the air pump.
• P2445 — Related to Secondary Air Injection System failure, addressed by TSB-0033-17 Rev1 on this platform.

Frequently Asked Questions