Experiencing your truck suddenly turning off while driving can be incredibly unsettling and, more importantly, dangerous. It’s a problem that leaves you stranded and scratching your head, especially when initial diagnostics don’t reveal any obvious culprits. One truck owner has shared their frustrating experience with a 2007 Toyota truck exhibiting this exact issue, and despite multiple professional opinions and part replacements, the mystery persists. Let’s delve into their journey and explore potential avenues for resolution.
The Mystery of the Vanishing Error Codes
The first hurdle in diagnosing this problem is the perplexing absence of error codes. Despite being assessed by three different mechanics and workshops, diagnostic scans consistently show no stored codes related to a major malfunction. This eliminates many common engine or system failures that typically trigger diagnostic trouble codes, leaving technicians and the owner in the dark. The only code detected was related to low tire pressure sensors, a long-standing and unrelated issue. This lack of diagnostic direction makes pinpointing the cause significantly more challenging.
Steps Already Taken: A Process of Elimination
Driven by the need to resolve this dangerous issue, the truck owner has already undertaken several troubleshooting steps, replacing components that are often linked to engine stalling or shutdown problems:
Crankshaft Position Sensor Replacement
Suspecting a faulty crankshaft position sensor, a common cause of intermittent engine issues, they replaced this component. Crucially, they ensured they obtained the correct sensor for their specific 2007 Toyota truck model using the VIN. However, this replacement led to an unexpected complication: the truck wouldn’t crank, and the engine kept turning over even after the key was turned off. This occurred with two different sensors, leading to the conclusion that the crankshaft sensor replacement, while a logical step, did not solve the original problem and may have introduced a new, albeit temporary, issue. The Toyota dealership confirmed that this sensor does not require programming, further deepening the mystery of why the new sensors prevented the engine from cranking normally.
Fuel Pump Replacement
Fuel delivery issues are another prime suspect in cases of sudden engine shutdown. To address this possibility, the fuel tank was dropped, and the fuel pump was replaced with a new one. Unfortunately, as noted, this also did not resolve the problem, confirming that the fuel pump was not the cause of the truck turning off while driving.
Wiring and Ground Checks
Electrical gremlins are notorious for causing intermittent and hard-to-diagnose problems in vehicles. A thorough check of the wiring for ground issues was performed, and everything was reported to be in good order. While this eliminates a broad category of potential problems, it doesn’t rule out more subtle wiring faults, such as intermittent shorts or breaks within the wiring harness itself.
Unidentified Engine Noise
Adding another layer to the puzzle, after the crankshaft sensor replacement attempts, a noise was heard under the hood during cranking. The exact location and nature of this noise remain undetermined, as it’s not audible from inside the vehicle. Whether this noise is related to the original issue or a consequence of the attempted sensor replacement is unclear, but it warrants further investigation.
Ruling Out Fuel Shut-Off Valve (Potentially)
Based on advice from a mechanic, a fuel shut-off valve issue was considered. However, the mechanic suggested that if this valve were the problem, the truck wouldn’t start at all. Since the truck does start and run, albeit with the issue of randomly shutting off, a complete fuel shut-off valve failure seems less likely, although an intermittent issue with this system cannot be entirely discounted.
Rodent Damage and Wiring Concerns
A relevant piece of information shared by a Toyota dealership is the potential for rodent damage to wiring. Toyota reportedly used a soy-based coating on their wires, which can attract rodents. While a visual inspection of the wiring has been conducted and no obvious rodent damage found “so far,” this remains a potential area of concern, especially for intermittent electrical problems. Rodents can cause damage in hard-to-see areas within wiring harnesses.
Potential Culprits and What to Check Next
Given the troubleshooting steps already taken and the persistent nature of the problem, here are some potential areas to investigate further:
- Intermittent Electrical Issues: While ground checks were performed, intermittent shorts or breaks in the wiring harness, particularly related to engine management sensors or the ignition system, can be incredibly difficult to pinpoint. A more detailed and dynamic wiring harness inspection might be necessary, potentially involving wiggle tests and voltage drop tests under load.
- Failing or Intermittent Relay or Sensor: Even if sensors are new, a faulty new part is always a possibility, albeit less likely. Beyond the crankshaft sensor, other sensors like the camshaft position sensor, mass airflow sensor (MAF), or even relays in the engine management system could be failing intermittently without always triggering codes.
- Ignition System Components: While less common in modern vehicles, issues within the ignition system itself, such as a failing ignition coil or module, could cause intermittent engine shutdowns.
- Fuel Delivery System (Beyond the Pump): While the fuel pump was replaced, other components in the fuel delivery system could be at fault. These include the fuel pressure regulator, fuel injectors (though usually causing rough running before complete shutdown), or even a blockage in the fuel lines.
- Computer (ECU/PCM) Malfunction: Though less frequent, an intermittent fault within the engine control unit (ECU) or powertrain control module (PCM) itself could cause unpredictable engine shutdowns. This is often a last resort diagnosis due to complexity and cost.
Seeking Community Wisdom
The truck owner in this scenario is understandably frustrated and facing significant financial concerns as a senior on a fixed income. Having already invested time and money into diagnostics and part replacements without success, the prospect of further expensive, hourly-rate troubleshooting at a dealership is daunting.
This situation highlights the challenges of diagnosing intermittent automotive problems, especially when error codes are absent. If you have experienced a similar issue with a truck turning off while driving, or have expertise in diagnosing such problems, your insights and suggestions would be invaluable. Sharing your knowledge could potentially help this truck owner and others facing similar frustrating automotive mysteries.
