Experiencing a no-start condition with your 2000 Dodge Ram 1500 can be frustrating, especially when coupled with a non-responsive OBD2 port. If you’re facing a situation where your trusty truck cranks strongly but refuses to fire up, and you notice a complete lack of power at your OBD2 diagnostic port, you’re in the right place. This guide will walk you through the diagnostic steps to pinpoint why your 2000 Dodge Ram 1500 has no power to the OBD2 port and won’t start.
Symptoms of No OBD2 Power and No Start in a 2000 Dodge Ram 1500
When your 2000 Dodge Ram 1500 exhibits a no-power issue at the OBD2 port alongside a no-start condition, several key symptoms often present themselves:
- Engine Cranks But Won’t Start: The starter motor engages, and the engine turns over, indicating the battery and starter system are functional. However, the engine fails to ignite and run.
- No Dashboard Lights: Typically, when you turn the ignition key to the ‘ON’ position, various dashboard warning lights illuminate momentarily. In this scenario, there’s a complete absence of these lights, suggesting a broader electrical issue.
- Interior Lights May Also Be Off: While less definitive, the lack of interior lights can further support the theory of a power supply problem affecting multiple vehicle systems.
- Non-Functional OBD2 Port: Attempting to connect a scan tool to the OBD2 port yields no response. The scanner fails to power up or establish communication with the vehicle’s computer system, confirming the lack of power at the port.
These symptoms, especially the combination of no-start and no OBD2 power, strongly indicate a fundamental electrical supply problem affecting critical engine management and diagnostic systems.
Investigating the Cause: No Power to OBD2 and No Start
Let’s delve into the potential causes behind the lack of power to your OBD2 port and the subsequent no-start issue in your 2000 Dodge Ram 1500. We’ll follow a logical diagnostic path, starting with the simpler possibilities and progressing to more complex components.
1. Fuse Inspection: The First and Easiest Check
Fuses are designed to protect electrical circuits from overloads. A blown fuse is a common cause of localized power loss.
- Locate Fuse Boxes: Your 2000 Dodge Ram 1500 will have at least one, possibly two fuse boxes. Common locations are under the dashboard and in the engine compartment. Consult your owner’s manual for precise locations.
- Identify Relevant Fuses: Look for fuses related to the Powertrain Control Module (PCM), ignition system, and diagnostic systems. Fuse box diagrams (usually printed on the fuse box cover or in the owner’s manual) are crucial here. Specifically, check fuses that supply power to the OBD2 port and the PCM.
- Inspect Fuses: Visually inspect each fuse. A blown fuse typically has a broken filament inside. For a more definitive check, use a fuse tester or a multimeter to confirm continuity.
- Replace Blown Fuses: If you find any blown fuses, replace them with fuses of the exact same amperage. If the replacement fuse blows immediately, it indicates a more serious short circuit in the system that needs further investigation.
2. Power Supply to the OBD2 Port
If the fuses are intact, the next step is to directly check for power at the OBD2 port itself.
- Locate Pin 16: The OBD2 port’s pin 16 is designated for battery voltage (12V power). It should be located at the top right corner of the connector.
- Voltage Test: Use a multimeter set to DC voltage. Ground the black lead of the multimeter to a known good ground point on the vehicle chassis or negative battery terminal. Probe pin 16 of the OBD2 port with the red lead.
- Expected Reading: You should read battery voltage (approximately 12V) at pin 16. If there’s no voltage, or significantly lower voltage, this confirms a power supply issue to the OBD2 port.
3. Investigating the PCM Power Supply and ASD Relay
Since the original post mentions no spark and suspects the PCM, let’s investigate the PCM’s power supply and the Auto Shutdown (ASD) relay, which is critical for engine operation.
- PCM Power Fuses and Relays: Refer to wiring diagrams for your 2000 Dodge Ram 1500 to identify fuses and relays that directly power the PCM. Check these fuses and the ASD relay in the same manner as described in step 1.
- ASD Relay Function: The ASD relay is typically controlled by the PCM and supplies power to vital engine components, including the ignition coil, fuel injectors, and PCM itself in some configurations. A faulty ASD relay can cut power to these systems, causing a no-start and potentially affecting PCM operation.
- ASD Relay Testing:
- Swap Test: If possible, swap the ASD relay with an identical relay from a less critical system (like the horn relay, if applicable). If the issue resolves, the ASD relay is likely faulty.
- Voltage Test at Relay Socket: Identify the power supply pin at the ASD relay socket (using wiring diagrams). Check for voltage at this pin with the ignition ON. Also, check for ground at the control pin when the PCM should be activating the relay.
- PCM Power Input Check: Consult wiring diagrams to identify the power input pins on the PCM connector. Using a multimeter, check for battery voltage at these pins with the ignition ON. Lack of power to the PCM is a serious issue and could explain the no-start and OBD2 problems.
4. Ignition Coil and PCM Driver Circuit
The original poster checked for spark and diagnosed power to the coil, suspecting a PCM driver issue. Let’s consider this further.
- Coil Power and Ground: Verify power is reaching the ignition coil (as per the original post, power was present). The coil also needs a ground signal from the PCM to fire the spark plug.
- PCM Driver Signal: The PCM controls spark by grounding the coil driver circuit. As noted in the original post, a test light flickered dimly on the driver side. A weak or absent ground signal from the PCM could prevent spark.
- PCM Driver Failure: A faulty PCM driver circuit within the PCM can be the root cause of no spark, even if power and sensor signals are present. While less common than fuse or relay issues, PCM failure is a possibility, especially in older vehicles or those with a history of electrical modifications as mentioned in the background.
5. Crankshaft and Camshaft Sensors
The original diagnostic results indicate signals present from the Crankshaft Position Sensor (CKP) and Camshaft Position Sensor (CMP). These sensors are crucial for the PCM to determine engine position and timing for spark and fuel injection. While signals were reportedly present, it’s worth noting that:
- Signal Integrity: A scoped signal present doesn’t guarantee signal integrity. A weak or noisy signal could still confuse the PCM. Double-checking sensor signals with a scope or using a scan tool (if communication can be established) to monitor live data can be beneficial.
- Sensor Wiring: Inspect the wiring and connectors for the CKP and CMP sensors for damage, corrosion, or loose connections.
Conclusion: Diagnosing No OBD2 Power and No Start on a 2000 Dodge Ram 1500
Based on the diagnostic steps and the information from the original post, the most likely areas to focus on for a 2000 Dodge Ram 1500 with no OBD2 power and a no-start condition are:
- Power Supply Issues: Start with fuses and relays, particularly those related to the PCM, ignition, and OBD2 port. Thoroughly test the ASD relay and PCM power supply.
- PCM Malfunction: If power supply issues are ruled out, a faulty PCM becomes a prime suspect, especially given the no-spark condition and the weak driver signal observed in the original post.
- Wiring and Connectors: Carefully inspect wiring harnesses and connectors related to the PCM, OBD2 port, ignition system, and sensors for any signs of damage, corrosion, or poor connections. The customer’s note about recent electrical work raises the possibility of wiring issues introduced during those modifications.
Systematically working through these diagnostic steps will help you pinpoint the cause of the no OBD2 power and no-start issue in your 2000 Dodge Ram 1500. If PCM replacement is suspected, ensure thorough diagnosis beforehand, and consider professional programming or flashing of the new PCM if required for your vehicle. Remember to consult vehicle-specific wiring diagrams and repair manuals for accurate testing procedures and component locations for your 2000 Dodge Ram 1500.
