Check Engine Light On But No Codes? Troubleshooting for Dodge Vehicles
If the check engine light is on but your scanner shows no codes, you may be dealing with poor scan tools, pending/permanent codes, or communication issues. This consolidated guide explains how to read hidden data, use the ignition key trick on legacy models, and decide when to seek professional help.
1. Confirm Using a Quality Scanner
- Ensure your scanner reads pending, permanent, and manufacturer-specific codes.
- Use all-module scan: PCM, TCM, ABS, and BCM can each store faults that trigger the MIL.
- Review freeze-frame data, fuel trims, and Mode 06 test results-basic readers can’t access these.
2. Ignition Key Trick (Legacy Dodge Models)
- Works on many 1996-2003 Dodges. Cycle ignition ON-OFF-ON-OFF-ON (without starting).
- Codes display on the odometer or as MIL flashes (two-digit format). Long pauses separate codes.
- Code 55 (five flashes, pause, five flashes) indicates the end of the list.
- Use this to capture basic codes if the scanner fails, but confirm with an OBD-II tool afterward.
3. Inspect Communication & Wiring
- Check DLC (diagnostic connector) pins for bending, corrosion, or pushed-back terminals.
- Inspect wiring for aftermarket accessories (remote starts, tuners) that splice into the communication network.
- Low battery voltage or failing alternators cause communication faults-test the charging system.
4. Pending/Permanent Codes and Readiness
- Pending codes set when a fault occurs but hasn’t met the threshold for a stored code. A second drive cycle may store it.
- Permanent codes remain until the PCM verifies the repair during specific drive criteria-clearing with a scanner won’t remove them.
- Readiness monitors reset to NOT READY after clearing codes or battery disconnects; complete a drive cycle before inspection.
Frequently Asked Questions
Can the MIL turn on without a readable code?
Yes. Pending/permanent codes or module-specific faults may not appear on basic readers. Use a higher quality scanner or have a shop read the codes.
Should I clear the light if no code shows up?
No. Clearing hides the symptom without fixing the cause. Diagnose voltage, communication, or pending code issues first.
When should I take the vehicle to a professional?
If you cannot retrieve codes with a quality scanner, if multiple modules show communication errors, or if the MIL returns immediately, schedule a professional diagnosis.
Need a full diagnostic workflow? Review the Dodge check engine light guide and model-specific articles for detailed testing steps.
When to Seek Professional Help
Professional scan tools can access advanced data, perform bidirectional tests, and capture intermittent communication faults that consumer tools miss. If the MIL persists without readable codes, let a qualified technician investigate.