Chrysler-specific code — factory diagnostic data| DTC Data Sheet | |
| Code | P0406 — EGR position sensor circuit high |
| Platform covered | Chrysler LX — 300, 300C, 300 Touring, 300C SRT-8, Dodge Charger, Dodge Magnum |
| Model years | 2005–2010 |
| Engines referenced in the circuit | 2.7L V6 (EER), 3.5L V6 (EGG), 5.7L HEMI MDS (EZB) — ground-circuit routing differs between V6 and V8 |
| System | Powertrain / Emissions (EGR) |
| Fault type | Circuit High |
| Monitor conditions | Ignition ON, battery voltage greater than 10 V |
| Set condition | EGR position sensor signal greater than 4.89 V. One-trip fault. |
| Special tool required | Miller #8815 PCM pinout box. Do not probe PCM harness connectors directly — probing damages PCM terminals and causes follow-on faults. |
| Scan tool | DRB III, wiTECH, or aftermarket OBD-II with live data |
Scope note. P0406 on the LX platform shares the same EGR circuit topology across Chrysler 300 / 300C / 300 Touring / 300C SRT-8, Dodge Charger, and Dodge Magmum. The ground circuit routes differently for 2.7L / 3.5L V6 (via splice S121 / S106 and C100 pin 13) versus 5.7L HEMI (via S110 / S115 / S116 and C100 pin 16, landing at G102) — the diagnostic procedure below works the same for both, but expect different splice labels when tracing the ground circuit on a V6 vs a V8.
P0406 means the PCM is reading the EGR position sensor signal at or above the 4.89 V set threshold — a value the sensor should never produce in normal operation, since the sensor runs on a 5 V reference and its output spans roughly 0.2 V (valve closed) to 4.5 V (valve fully open) during commanded EGR actuation. When the PCM sees the signal pinned near the 5 V rail, it knows the circuit is electrically wrong — a short to a supply voltage, an open on the ground leg, or a failed sensor inside the EGR solenoid assembly — not a mechanical EGR flow problem. This is a one-trip fault on the LX platform: the PCM sets P0406 and illuminates the MIL on the first drive cycle the condition is present.
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P0406 Chrysler 300C Quick Answer
Verify the EGR position sensor actually reads above 4.5 V with the engine running. If confirmed, work the factory sequence in order: check the signal wire for a short to the 5 V supply, then for a short to battery voltage; jumper the signal to sensor ground to verify whether the sensor itself is reporting wrong; then check the signal wire and the sensor ground wire back to the PCM for opens using the Miller #8815 pinout box. PCM is the last suspect. Never probe the PCM harness connectors directly — the factory procedure mandates the #8815 pinout box to protect the PCM terminals.
The Diagnostic Procedure
Tools: scan tool with live data (DRB III, wiTECH, or aftermarket with Chrysler coverage), DMM capable of measuring <100 Ω resistance accurately, jumper wire, Miller #8815 PCM pinout box.
Pin mapping — each wire in the diagram above has a Chrysler circuit ID (K-, F- and Z- prefixes), a gauge, and an insulation-color abbreviation. Keep this table handy while working through the steps:
- EGR connector pin 1 = EGR signal (circuit K34, 20 AWG, DB/LG) | goes to PCM connector C2 pin 22
- EGR connector pin 2 = 5 V supply (circuit F856, 20 AWG, YL/PK) | comes from PCM connector C1 pin 27
- EGR connector pin 3 = sensor ground (circuit K900, 20 AWG, DB/DG) | returns to PCM connector C2 pin 27
- EGR connector pin 4 = chassis ground (circuit Z904, 14 AWG, BK/BR) — routes to G102 via splice S116 on 2.7/3.5L, via S115 + S116 on 5.7L HEMI
- EGR connector pin 6 = EGR solenoid control (circuit K35, 20 AWG, DB/VT) | driven by PCM connector C2 pin 8
Pin numbers are embossed on the connector housings next to each cavity; orient the connector with its locking tab facing you to read them correctly.
- Confirm EGR position sensor voltage is above 4.5 V. Start the engine. With the scan tool, read the EGR Position Sensor voltage.
→ Above 4.5 V: fault is current, proceed to step 2.
→ Below 4.5 V: intermittent — follow the intermittent-condition procedure and run the Powertrain Verification Test. - Check the K34 signal circuit for a short to the 5 V supply. Ignition OFF. Disconnect the EGR solenoid harness connector AND the PCM harness connectors. Measure resistance between pin 1 (EGR signal) and pin 2 (5 V supply) at the EGR solenoid harness connector.
→ Resistance below 100 Ω: short present between the signal wire and the 5 V supply. Repair the short. Retest.
→ Resistance above 100 Ω: proceed to step 3. - Check the K34 signal circuit for a short to battery voltage. Ignition ON, engine not running. Measure voltage on pin 1 (EGR signal) at the EGR solenoid harness connector (connector still disconnected from the EGR assembly).
→ Voltage above 0 V: short to battery on the signal wire. Repair and retest.
→ 0 V: proceed to step 4. - Test the EGR solenoid assembly with a known-good signal. Ignition OFF. Reconnect the PCM harness connectors. Connect a jumper wire between pin 1 (EGR signal) and pin 3 (sensor ground) at the EGR solenoid harness connector (effectively replacing the sensor’s output with a clean ground reference). Ignition ON, engine not running. Monitor EGR Position Sensor voltage on the scan tool.
→ Voltage below 0.5 V: the PCM and wiring are fine; the EGR solenoid assembly’s internal position sensor is the fault. Replace the EGR solenoid assembly. Remove the jumper wire first.
→ Voltage still high: fault is PCM-side. Remove the jumper wire and proceed to step 5. - Check the K34 signal circuit for an open. Ignition OFF. Disconnect the PCM harness connectors. Install Miller Special Tool #8815 PCM pinout box — do NOT probe the PCM connectors directly. Measure the resistance of the K34 EGR signal circuit from EGR connector pin 1 through the harness to PCM C2 pin 22 on the #8815 pinout box.
→ Resistance below 5.0 Ω: wire is intact, proceed to step 6.
→ Resistance above 5.0 Ω: open in the signal wire. Repair and retest. - Check the K900 sensor ground circuit for an open. Using the same #8815 setup, measure resistance of the K900 sensor ground circuit from EGR connector pin 3 through the harness to PCM C2 pin 27 on the #8815 pinout box.
→ Resistance below 30 Ω: sensor ground is intact, proceed to step 7.
→ Resistance above 30 Ω: open in the ground wire. Repair and retest. - PCM inspection / replacement. Before condemning the PCM, inspect the PCM harness connector terminals for corrosion, damage, or pushed-out pins. Use the schematics as a guide and pay particular attention to all power and ground circuits on the PCM connectors.
→ Wiring / terminal problem found: repair and retest.
→ No problems found: replace and reprogram the PCM per the service information, then run the Powertrain Verification Test.
Professional tip. Step 4’s jumper trick is diagnostically elegant — by shorting the signal line to sensor ground, you replace the EGR sensor’s unknown output with a known-good 0 V reference. If the scan tool now reads near 0 V, the wiring from the EGR connector back to the PCM is reading correctly, which means the fault is inside the sensor (replace the EGR solenoid assembly). If the scan tool still reads high despite the jumper, the signal wire itself or the PCM is reading wrong — move to the Miller #8815 checks. Doing step 4 first avoids unnecessary PCM probing.
Common Causes on LX Platform Vehicles
The factory procedure lists six possible causes for P0406, in diagnostic order. Each is isolated by a specific step:
- K34 EGR position sensor signal circuit shorted to F856 5 V supply circuit — isolated by step 2. Usually a chafed wire in the engine bay harness contacting the 5 V reference line.
- K34 EGR position sensor signal circuit shorted to battery voltage — isolated by step 3. Harness damage routing the signal wire against a power-feed conductor.
- K34 EGR position sensor signal circuit open — isolated by step 5. Broken wire, backed-out terminal, or corroded pin between the EGR connector and the PCM.
- K900 sensor ground circuit open — isolated by step 6. Break in the sensor-ground return between the EGR connector and the PCM; pulls the sensor output toward the 5 V rail because the reference is floating.
- EGR solenoid assembly — isolated by step 4. Internal fault in the integrated position sensor inside the EGR solenoid assembly. Replacement is at the whole-unit level.
- PCM — step 7. Last candidate after all wiring, terminal, and sensor checks pass.
Severity & Driving
P0406 disables closed-loop EGR feedback: the PCM can no longer verify the EGR valve’s commanded position, so it falls back to a safe default EGR strategy (commanding minimal or no EGR flow). Practical consequences are mild — slightly elevated combustion temperatures under load (possible light pinging on 87 octane), a modest increase in NOx emissions, and failed state emissions inspection. No immediate safety concern; continued driving to a workshop is fine. The MIL will stay on until the fault is repaired and the PCM runs a good drive cycle.
FAQ
Does this apply to my Dodge Charger or Dodge Magnum?
Yes. P0406 on the LX platform uses the same EGR circuit topology across Chrysler 300 / 300C / 300 Touring / 300C SRT-8, Dodge Charger, and Dodge Magnum (2005–2010). The ground-circuit route differs slightly between V6 (2.7L / 3.5L) and V8 (5.7L HEMI), but the diagnostic procedure is the same for both — only the splice labels change when tracing the ground wire.
Why does the procedure insist on the Miller #8815 pinout box?
Because the PCM harness connector uses fine-pitched terminals that spread permanently when probed with a standard DMM lead. Spread terminals lose tension against the mating pin, producing intermittent circuit faults that set new DTCs over the next weeks or months — a classic way a P0406 diagnosis turns into a multi-code headache. The #8815 presents the PCM connectors through a pinout box with proper test points so the original terminals stay untouched. If you don’t have the #8815, work only the EGR-side measurements in steps 2–4 and leave the wire-integrity checks to someone who does.
What’s the difference between P0405 and P0406?
P0405 is the same EGR position sensor circuit reporting low (stuck near 0 V when the valve should be reporting open); P0406 is the circuit reporting high (stuck near the 5 V rail). Same components, opposite electrical failure modes, and similar diagnostic approach but reversed polarity on the short-test direction. Don’t apply this P0406 procedure to P0405 without consulting the P0405-specific service information.
Is the EGR solenoid assembly the same thing as the EGR valve?
On the LX platform the “EGR solenoid assembly” is the complete EGR unit with integrated position sensor and PCM-controlled electrical actuation — it combines what older systems split into separate valve and solenoid components. If step 4’s jumper test points at the sensor, you replace the whole assembly, not just an internal sensor.
Why is P0406 a one-trip fault when most emissions codes need two trips?
Because P0406 is a direct electrical fault, not an operational monitor. When the sensor reports out-of-range voltage, the PCM knows immediately that the circuit is electrically wrong — there’s no multi-cycle monitoring to perform. Compare P0430 catalyst efficiency, which requires two consecutive drive cycles because the catalyst monitor has to run through its full observation window before passing judgment. Electrical faults are judged instantly; efficiency judgments are not.