2013–2024 RAM 2500/3500 6.7 Cummins Cold Start / Grid Heater Path
On 2013–2024 RAM 6.7 Cummins, prove battery and grid heater power delivery under load before replacing the heater or moving to fuel system diagnosis.
Fault Overview
Platform-specific diagnostic path for cold start and grid heater issues on 2013–2024 RAM with 6.7 Cummins. Integrates common SPNs, observed patterns, and known failure modes for this application. Always consult current Cummins and RAM service literature by VIN for platform-specific service information.
Engine & Platform Coverage
Symptoms
- •RAM 6.7 hard start in cold weather
- •Cummins grid heater failure
- •RAM white smoke on cold start
- •6.7 no-start in freezing conditions
- •Grid heater connection fault on RAM
Possible Causes
- 1.Grid heater element failure including hardware integrity issues
- 2.High-current cable and connection voltage drop
- 3.Relay faults
- 4.Battery capacity issues common on dual-battery systems
- 5.Glow strategy interaction on later calibrations
- 6.Fuel quality and lift pump performance exaggerated when cold
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
6 steps locked behind Technician Mode- 1Step 1 — Battery and Cranking Voltage Test: Test both batteries on dual-battery systems individually and as a system. Measure cranking voltage during start attempt. A weak battery in a dual-battery system can cause cold-start issues that appear to be heater-related.
- 2Step 2 — Wait-to-Start and Heater Command Confirmation: Confirm the wait-to-start lamp operates correctly and the ECM is commanding the grid heater. Verify heater command duration is appropriate for ambient temperature.
- 3Step 3 — Voltage and Current at Grid Heater Under Load: Measure voltage at the grid heater positive stud and current draw under commanded load. Voltage must be near battery voltage. Voltage drop at the stud connections is a documented issue on this platform.
- 4Step 4 — Full Voltage-Drop Test on High-Current Paths: Perform a complete voltage-drop test on all high-current paths including battery cables, relay, and heater connections. Total drop should be below 0.5 V.
- 5Step 5 — Element Resistance and Physical Inspection: Measure element resistance cold. Inspect the heater physically for damage or hardware integrity issues. Consult current service information for any revised parts or procedures for the specific model year.
- 6Step 6 — Fuel Pressure During Cold Crank: If electrical is proven good, measure fuel pressure during cold cranking. Lift pump performance and fuel quality issues are exaggerated in cold conditions on this platform.
- 7Step 7 — Check for Related Codes and TSBs: Retrieve all active and pending codes. Check for applicable TSBs for the specific model year regarding heater replacement procedures and any revised parts.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
3 steps locked- 1Replace grid heater with updated hardware where applicable per current service information.
- 2Service battery cables and connections with excessive voltage drop.
- 3Replace relay if confirmed failed.
- 4Service batteries if capacity is insufficient.
- 5Address fuel delivery issue if pressure is low during cold crank.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
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Related Fault Codes
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Summary
On 2013–2024 RAM 6.7 Cummins, prove battery and grid heater power delivery under load before replacing the heater or moving to fuel system diagnosis.