🚨 Diagnostic Profile
Vehicle Make: BMW
Code/Module: DM-TL (Diagnostic Module – Tank Leakage)
Description: This fault indicates a Signal High condition on the Pump Control Circuit of the Tank Leakage Diagnostic Module, commonly referred to as the EVAP Leak Detection Pump (LDP) module. This module is responsible for pressurizing the fuel tank system to detect evaporative emission leaks. A “Signal High” fault typically points to a short to voltage (battery positive) on the control wire, a sticking relay inside the module, or an internal module failure causing the feedback circuit to read higher voltage than expected.
🚨 Repair Difficulty Tier
Rating: [Intermediate]
This repair requires the use of a BMW-specific diagnostic scan tool (such as ISTA/D) to read live data and fault freeze frames, along with a digital multimeter to test wiring integrity and voltage values at the module connector. While no major structural disassembly or airbag/restraint systems are involved, proper identification of short-to-power circuits versus internal module failure requires intermediate electrical diagnostic skill.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Visually inspect the DM-TL module location (typically near the fuel tank, under the rear of the vehicle) for signs of physical damage, corrosion, or water intrusion in the electrical connector.
- Check the connector pins for bent or corroded contacts that could cause a false high signal.
- Inspect the wiring harness between the module and the DME/ECU for chafing, pinching, or exposed wires that could be shorting to a power source (such as battery positive or the main relay feed).
- Confirm battery voltage is within normal range (12.4V – 12.8V at rest) since low or fluctuating voltage can skew sensor signal readings.
Step 2: Diagnostic Verification
- Connect a BMW-capable scan tool (ISTA/D, Autel, or equivalent) and pull live data for the DM-TL Pump Control Circuit voltage reading.
- With the key on and engine off, verify if the pump control circuit shows a constant high voltage (close to battery voltage) even when the module is commanded off — this confirms a Signal High condition.
- Using a multimeter, backprobe the control circuit wire at the module connector and check for voltage with the module electrical connector disconnected. If voltage is still present, this confirms a short to power in the harness rather than an internal module fault.
- If no voltage is present with the connector disconnected, but the fault returns when reconnected, this points toward an internal module relay/pump failure.
Step 3: Resolution & Reset Process
- If a wiring short to power is found, repair or replace the damaged harness section and ensure proper insulation/loom protection is reinstalled.
- If the module itself is found to be faulty (common after high mileage or water intrusion), replace the DM-TL (Leak Diagnostic Pump) module as a complete unit—these are generally non-serviceable.
- After repair or replacement, clear the fault codes using the scan tool and perform a full EVAP system leak test/self-test cycle to confirm the module cycles correctly without re-triggering the Signal High fault.
- Perform a test drive with a drive cycle monitor to ensure the EVAP readiness monitor completes successfully and no additional codes return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: DM-TL Leak Diagnostic Pump Module, replacement wiring harness section/connector (if applicable), BMW-specific scan tool (ISTA/D or equivalent) for fault clearing and verification.
Average Component Price: $150 – $450 USD for the DM-TL module (OEM pricing varies by model year/chassis); wiring repair materials are typically under $50 unless a full harness section is required.
Estimated Labor Hours: 0.5 – 1.0 hour for diagnostic testing; 0.5 – 1.5 hours for module replacement or wiring repair, depending on accessibility near the fuel tank assembly.