P067A — Cylinder 4 Glow Plug Control Circuit Low #

Note: The code description may vary depending on the vehicle manufacturer.

• Cylinder 4 Glow Plug Circuit Low (Ford)
• Cylinder 4 Glow Plug Control Circuit Low (General Motors)
• Glow Plug Circuit Low Voltage, Cylinder 4 (Chrysler)

Summary of the P067A Code #

P067A is a diagnostic trouble code (DTC) that indicates a detected low voltage or resistance issue in the control circuit of the glow plug for cylinder 4. The glow plug is an electrically heated element in diesel engines, designed to assist with cold starts by preheating the combustion chamber. The control circuit refers to the wiring, connectors, and the relay or module that manages the electrical current delivered to the glow plug. This DTC is set by the engine control module (ECM) when it senses that the voltage in cylinder 4’s glow plug circuit is below the expected threshold, signaling a possible fault. While this code mainly affects diesel engines, it can be found across multiple vehicle makes and models. If left unresolved, this issue can impact engine starting and performance, especially in cold conditions.

Common Symptoms for Code P067A #

When the P067A code is active, drivers may notice symptoms especially during cold starts or in colder climates. The severity of these symptoms can vary, but ignoring them can lead to increased engine wear over time. It’s worth noting that these symptoms do not usually prevent the vehicle from running, but can make starting more difficult and lead to rough idle.

• Hard starting, especially in cold weather
• Rough idle immediately after starting
• Excessive white smoke from exhaust on startup
• Check engine light (MIL) illuminated
• Decreased engine performance until warm

Probable Causes of P067A (Most to Least Common) #

Several factors can trigger the P067A code. Understanding these causes can help narrow down the issue efficiently. Most commonly, it’s an electrical fault or a failed glow plug, but other underlying issues may also be to blame. Here’s the order of likelihood:

1. Faulty glow plug (cylinder 4)
2. Open or shorted wiring in the glow plug circuit
3. Loose, corroded, or damaged connectors
4. Defective glow plug control module or relay
5. ECM (Engine Control Module) failure (rare)

Step-by-Step Diagnostic Guide for P067A #

Diagnosing P067A requires a systematic approach to ensure you address the root cause and avoid unnecessary parts replacement. Safety first: always allow the engine to cool before working on glow plug circuits to avoid burns or electrical shock.

• Step 1: Scan for additional codes and record freeze frame data for context.
• Step 2: Visually inspect cylinder 4 glow plug, wiring, and connectors for signs of corrosion, damage, or loose connections.
• Step 3: Using a digital multimeter, check the resistance of the glow plug on cylinder 4 (compare to manufacturer specs).
• Step 4: With the ignition on (engine off), test for proper voltage at the glow plug connector.
• Step 5: Inspect the glow plug control module or relay for correct operation.
• Step 6: If all components check out, consider testing the circuit from the ECM to the glow plug for continuity and shorts.

Possible Repairs for P067A #

The repairs for this code are closely linked to the underlying cause identified during diagnostic steps. Always clear the code after repairs and test drive to ensure the issue is resolved.

• Replace the faulty glow plug (cylinder 4)
• Repair or replace damaged wiring or connectors in the circuit
• Clean corroded connections and apply dielectric grease
• Replace the glow plug control module or relay if defective
• In rare cases, repair or replace the ECM

Is It Safe to Drive with P067A? #

Limited: While it is usually possible to drive with the P067A code present, it is not recommended to ignore the issue—especially in cold weather. The primary risk is difficulty starting the engine, increased emissions, and potential long-term engine wear due to incomplete combustion at startup. If you live in a warm climate, the impact may be minimal, but in colder regions, prompt repair is strongly advised to avoid further complications.

Vehicles Most Commonly Affected by P067A #

This trouble code is primarily seen in diesel vehicles using electronically controlled glow plug systems. While it can appear in many makes, certain models and engines are more commonly affected due to the design of their glow plug circuits.

• Ford Powerstroke (6.7L, 6.4L, 6.0L diesel engines)
• Chevrolet/GMC Duramax (6.6L diesel engines)
• Ram/Cummins (6.7L diesel engines)
• Volkswagen TDI models
• Some Mercedes-Benz Bluetec diesels

Common Mistakes and Best Practices for P067A #

Misdiagnosis is frequent with glow plug codes, often leading to unnecessary parts replacement. Following a disciplined diagnostic method can save both time and money. Here are a few pitfalls to avoid and tips to ensure an accurate repair.

• Replacing all glow plugs without testing each one individually
• Overlooking corroded or loose connectors—always inspect and clean first
• Neglecting to check for wiring damage hidden under insulation or tape
• Resetting the code without addressing the root cause
• Assuming the ECM is faulty before checking all other components

Quick FAQ for P067A #

When this code appears, drivers and technicians often have a few immediate questions. Here are concise answers to the most common ones:

• Q: Will P067A cause my diesel to not start at all?
  A: In most cases, the engine will still start, but it may crank longer and run rough until warm—especially in cold weather.
• Q: Can I just clear the code and keep driving?
  A: Clearing the code without fixing the underlying issue may result in repeated hard starts and could eventually damage the engine or emission system. Always repair first, then clear the code.