1999 Dodge Intrepid Check Engine Light Guide
The 1999 Dodge Intrepid’s check engine light indicates the powertrain control module has stored a fault. Instead of comparing symptoms with other cars, retrieve the codes, follow a structured diagnostic flow, and confirm the fix before clearing the MIL to avoid costly surprises.
- Applies to: 1999 Intrepid 2.7L and 3.2L V6 models.
- Tools: OBD-II scanner, fuel pressure gauge, compression tester, EVAP smoke tester.
- Immediate action: If the MIL flashes, reduce throttle-active misfires can overheat catalytic converters.
Common 1999 Intrepid Codes
| Code | Subsystem | Likely Cause | First Checks | Estimated Repair (USD) |
|---|---|---|---|---|
| P0300/P030x | Misfire | Coil pack failure, fouled plugs, timing chain wear | Monitor misfire counters, inspect plugs/coils, perform compression test. | 200-450 for ignition components; 1,200+ if timing chain service needed. |
| P0128 | Coolant temperature | Thermostat stuck open, low coolant | Monitor warm-up profile, inspect thermostat housing, check coolant level. | 180-320 for thermostat replacement and coolant flush. |
| P0420/P0430 | Catalyst efficiency | Misfires, rich mixture, exhaust leaks | Compare upstream/downstream O2 patterns, inspect exhaust manifolds. | 1,000-1,900 per converter after upstream issues resolved. |
| P0455/P0456 | EVAP leak | Loose gas cap, cracked hoses, leak detection pump | Smoke-test EVAP, inspect cap seal, command purge solenoid. | 40-100 for cap/hoses; 350-600 for pump. |
| P0601/P0605 | PCM failure | Internal memory fault, voltage spikes | Verify charging voltage, inspect grounds, confirm via PCM diagnostics. | 600-900 for PCM replacement and programming. |
Diagnostic Workflow
- Scan and document: Record stored/pending codes, freeze-frame data, and Mode 06 results before clearing anything.
- Inspect basics: Check fluids, battery voltage, vacuum hoses, PCV system, and intake ducting.
- Assess fuel trims: Long-term trims beyond +/-10% indicate mixture issues-look for vacuum leaks or injector problems.
- Test suspect circuits: Wiggle-test wiring near coils and O2 sensors while watching live data; intermittent dropouts reveal harness faults.
- Verify mechanical health: Perform compression/leak-down tests if misfires persist-timing chain tensioner issues are common on high-mileage 2.7L engines.
- Confirm repairs: After resolving faults, clear codes with Mode $04$, complete a drive cycle, and verify readiness monitors return to COMPLETE.
Preventive Maintenance Tips
- Change engine oil every 3,000 miles (2.7L) to prevent sludge-related timing issues.
- Replace spark plugs and ignition wires at recommended intervals to prevent misfires.
- Inspect EVAP hoses during oil changes; replace the gas cap if the seal is cracked.
- Clean the throttle body and idle passages annually to stabilize idle control.
- Maintain battery and charging voltage; voltage spikes trigger PCM memory codes.
Frequently Asked Questions
Why does the light turn off after a few trips?
The PCM turns the light off after consecutive fault-free trips, but the code remains stored. Diagnose and repair the issue rather than assuming it is resolved.
Can I ignore an intermittent catalyst code?
No. Intermittent catalyst codes usually point to misfires or fuel control issues. Address them before the converter fails.
Will clearing the code lower repair costs?
Temporarily clearing the code without repairs often leads to more damage. Always fix the root cause before clearing the MIL.
Need more resources? Review the Dodge reset workflow and the Intrepid-specific article for additional diagnostics.
When to Consult a Professional
Seek professional diagnostics if timing chain wear is suspected, if PCM codes remain after basic checks, or if communication issues arise. Advanced testing protects the engine and emissions system from further damage.