1. Brake Booster Vacuum Leak:
* Mechanism: The brake booster uses engine vacuum to assist braking. A leak in the booster, vacuum lines, or the intake manifold can cause a significant drop in vacuum when the brakes are applied, leading to stalling. The engine needs the vacuum for various functions. When braking, the vacuum is suddenly drawn for assistance, and if there's a leak, the engine may lose enough vacuum to stall.
* Troubleshooting: Inspect all vacuum lines connected to the brake booster and intake manifold for cracks, holes, or loose connections. Listen carefully near the booster and lines while someone pumps the brakes; you might hear a hissing sound indicating a leak. A vacuum gauge can accurately check for proper vacuum.
2. Brake Light Switch:
* Mechanism: A faulty brake light switch can create a short circuit or an intermittent electrical problem. When the switch is depressed (brakes applied), it can disrupt the engine's electrical system, causing a stall. This is less common, but possible.
* Troubleshooting: Test the brake light switch for continuity and proper operation. A simple multimeter check can reveal if the switch is working correctly. This is often an easy and inexpensive part to replace.
3. PCM (Powertrain Control Module) Issues:
* Mechanism: A faulty PCM can misinterpret signals from various sensors, including those related to braking. This can lead to incorrect fuel delivery or ignition timing, causing a stall. This is less likely but a possible cause.
* Troubleshooting: This requires more advanced diagnostics. A professional scan tool is needed to check for diagnostic trouble codes (DTCs) stored in the PCM. The codes can point towards the specific problem.
4. Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP):
* Mechanism: These sensors tell the PCM the position of the crankshaft and camshaft. If they're failing or intermittently failing, they can cause misfires or stalling, especially when the engine is under load (like when braking). The heat might exacerbate a pre-existing problem in these sensors.
* Troubleshooting: These require a scan tool and potentially sensor testing with an oscilloscope (for more precise readings). A failing sensor will often throw a diagnostic trouble code.
5. Alternator or Battery Issues (Less Likely):
* Mechanism: While less probable, a failing alternator could cause voltage drops, leading to stalling, especially under a high electrical load (like the brake lights and booster). A weak battery might also contribute.
* Troubleshooting: Test the alternator's output voltage and the battery's charge.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any codes stored in the PCM. This is the first crucial step.
2. Inspect Vacuum Lines: Pay close attention to the brake booster and its connections.
3. Test the Brake Light Switch: Simple electrical test.
4. Check Battery and Alternator: Ensure proper charging system function.
Important Considerations:
* Safety First: If your vehicle is stalling when braking, it's a serious safety hazard. Drive cautiously and seek professional help immediately.
* Professional Diagnosis: If you're not comfortable performing these checks, take your vehicle to a qualified mechanic for diagnosis and repair. This is especially crucial for PCM, CKP, and CMP sensor related issues.
By systematically investigating these potential causes, you can narrow down the source of the problem and get your Dodge Ram back on the road safely. Remember to address this issue promptly due to the safety implications.
