The first-generation Chrysler 300C (LX platform, 2005–2010) is a rear-drive sedan built in the DaimlerChrysler era, and that heritage shapes its diagnostics: it borrows several components from the Mercedes E-Class of the time — most visibly the W5A580 5-speed automatic — while its electrical architecture is pure Chrysler, built around a central power-distribution module and split CAN buses. A lot of the 300C's faults are manufacturer-specific body, chassis, and network codes a basic reader can't fully decode. This guide groups the most common 300C trouble codes by system, explains what each means, and points to where a generic OBD-II reader stops and a Chrysler-capable tool is needed.
Which 300C do you have? The LX 300/300C came with the 2.7L and 3.5L V6, the 5.7L HEMI V8 (with MDS cylinder deactivation), and the 6.1L HEMI in the SRT8; a 3.0L CRD turbodiesel was sold in Europe. The base V6s generally used a 42RLE 4-speed, while the HEMI — and many AWD and later V6 cars — used the Mercedes-derived W5A580 5-speed; rear-wheel drive was standard with optional all-wheel drive. (Strictly, "300C" is the HEMI trim, but these codes apply across the LX 300 range.) The 300C shares its LX platform with the Dodge Charger and Magnum — the Challenger is the closely related LC platform — so most of these codes apply across those cars too. Behaviour varies by engine and drivetrain, so match a code to your car.
How Chrysler 300C fault codes are structured
The 300C uses the standard SAE OBD-II categories — P (powertrain), B (body), C (chassis), and U (network) — but a large share of its faults are manufacturer codes stored in individual modules that a basic reader can't see. The car runs two CAN buses: a high-speed CAN-C for powertrain/chassis and a lower-speed CAN-B for body/interior, tied together through a gateway. Chrysler's dealer tools of the era (StarSCAN / StarMOBILE, later wiTECH) read every module and expose sub-type detail and bidirectional tests a generic Mode 01 tool cannot.
One area sits behind a surprising number of 300C electrical faults: the central power-distribution and body-control electronics — on these early LX cars the Front Control Module (FCM) mounted on the power-distribution centre. A failure there can throw seemingly unrelated codes — fuel pump, lighting, cabin heater, no-start — at once, so when several unrelated electrical codes appear together it's worth checking what they share before replacing parts. See why low voltage causes multiple DTC codes and how to find the root-cause code.
Powertrain codes (engine & transmission)
Powertrain P-codes are the ones a generic OBD-II reader will usually catch. The most common on the 300C:
- P0300 — random/multiple misfire, with cylinder-specific codes P0301 through P0306 (V6) or to P0308 on the V8. On the 5.7L HEMI a frequent cause is the MDS (Multi-Displacement System) lifters and cam — the well-known "HEMI tick" — alongside the usual coils and spark plugs. Without a scanner, see how to find a misfiring cylinder without a scanner; with one, use scan-tool misfire diagnosis.
- P0016 — crankshaft/camshaft correlation, and P0339 — intermittent crankshaft position signal. Test as covered in crank & cam sensor testing.
- P0420 / P0430 — catalyst efficiency below threshold, banks 1 and 2. Confirm with the downstream O2 data before condemning a converter — P0420 diagnosis.
- P0128 — coolant below thermostat regulating temperature; a stuck-open thermostat is the usual cause (P0128 guide).
- P0455 — large EVAP leak; the gas cap and purge/leak-detection components are common causes (EVAP diagnosis).
- P0521 — engine oil pressure sensor range/performance; verify actual pressure with a mechanical gauge before replacing the sender.
- P0201 — injector circuit, cylinder 1; test the injector electrically per injector testing.
- P0562 — system voltage low, often the first domino in a charging or power-distribution problem.
On the transmission side, P0700 is a general "transmission control system" flag telling you the TCM has stored its own code — read the TCM for the specific fault, and start with fluid level and condition (automatic transmission code diagnosis). The Mercedes-derived W5A580 is sensitive to fluid condition, and its 13-pin transmission connector is a known leak point.
ABS, brakes & steering codes
Chassis C-codes are read through the ABS/ESP module, not the engine ECU, so a generic reader usually can't see them:
Climate (HVAC) codes — the 300C's common one
The LX cars are well known for HVAC blend-door and mode-door actuator failures, which show up as a clicking or tapping behind the dash, no heat or A/C on one side, or a temperature that won't change. These are body codes read through the automatic temperature control (ATC) module:
- B10A5 (left blend-door control circuit open), B10A8 (left blend-door actuator performance), and B10A9 (right blend-door control) — the classic split-temperature complaint.
- B1040 (panel/mode door) and B1058 (recirculation door) cover the other HVAC actuators. The actuators themselves are the usual failure; confirm the control circuit before assuming the ATC module.
Airbag (SRS) & body codes
300C B-codes split into genuine circuit faults you can diagnose and historical records you should not chase. Circuit faults (open, short, high/low resistance) are real wiring or component problems; crash/deployment records are historical. Common examples:
- B106C — curtain-airbag circuit resistance high (driver side). Squib circuits demand care; work with the battery disconnected and follow SRS precautions (diagnosing SRS airbag faults).
- B1200 / B1202 — airbag warning-indicator circuit low / open (the dash warning-lamp driver, not the airbag itself).
- B1476 — IG1 voltage extraordinarily low, and B10B4 — cabin-heater control circuit (driven through the power-distribution electronics). Both are power-delivery faults that point back at charging and power-distribution health.
Network (U) codes and lost communication
U-codes mean one module has stopped hearing another over the CAN network. On the 300C the split CAN-B / CAN-C architecture makes the bus itself a common culprit, often alongside a low-voltage condition:
- Bus-wiring codes U0001 (high-speed CAN-C) and the U0019–U0026 CAN-B circuit codes point at the bus wiring, power/ground, or termination rather than a single module — diagnose the bus with CAN bus fault diagnosis and the 60-ohm rule first.
- "Lost communication" codes such as U0100 (ECM/PCM), U0101 (TCM), U0121 (ABS), and U0143 (body control module) usually mean a module has dropped offline from a power, ground, or connector fault.
- U0167 / U0168 — lost communication with the vehicle immobilizer / security module, worth knowing on a no-start with security-light behaviour.
When you need a Chrysler-capable scan tool
A basic reader will pull generic powertrain P-codes, but most of the 300C's body, chassis, HVAC, and network faults live in modules a generic tool can't reach — and many repairs (actuator relearns, steering-angle initialisation, bidirectional tests) need dealer-level access. For those you'll want a Chrysler-capable scanner (the StarSCAN / StarMOBILE / wiTECH lineage, or an aftermarket tool with full Chrysler coverage). For the general workflow of turning a code into a confirmed fault, see why you should stop replacing parts without testing.
FAQ
What is the most common fault code on a Chrysler 300C? Misfire codes (P0300 and cylinder-specific P030x, often MDS-lifter-related on the HEMI) are among the most frequent, along with HVAC blend-door codes (B10A5), catalyst efficiency (P0420), and — on higher-mileage cars — wheel-speed and power-distribution-related electrical codes.
Why is there clicking behind my 300C dashboard / no heat on one side? That's the classic LX blend-door / mode-door actuator failure, which sets ATC body codes such as B10A5 or B1040. The actuator itself is usually at fault; confirm the control circuit before replacing the ATC module.
Can I read 300C codes with a cheap OBD2 scanner? A cheap reader will show generic engine (P) codes, but most B, C, and U codes — HVAC, ABS, airbag, network — need a Chrysler-capable tool (wiTECH-lineage or an aftermarket scanner with full Chrysler coverage) to read and to run the relearns repairs require.
Several unrelated electrical codes appeared at once — what causes that? On the 300C a weak battery/charging system or a failing power-distribution module can trigger multiple, seemingly unrelated codes together. Check power, grounds, and what the affected modules share before replacing anything — see the low-voltage cascade effect.