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Volvo Renault MID 140 PSID 227 FMI 12 Air Dryer APM Communication Fault

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User question

mid 140 psid 227 fmi 12

Artificial Intelligence Response

Direct answer to the question

  • Meaning: MID 140 PSID 227 FMI 12 = The instrument cluster (MID 140) reports a communication failure on the data channel to the Air Processing Module / air dryer unit (APM, typically MID 185). FMI 12 = “Bad intelligent device/component,” i.e., no/invalid communication from the APM.
  • Key points:
    • Most common causes: open/shorted CAN lines, corroded/loose connectors, loss of APM power/ground, or a failed APM.
    • Do not ignore: air system faults can escalate to brake warnings or “stop” conditions.

Detailed problem analysis

  • Architecture
    • MID 140 (dashboard/cluster) monitors network health and flags when a node like the APM (air dryer controller) drops off or talks invalidly.
    • The APM manages purge/regeneration, pressure control, and provides status over the high‑speed vehicle datalink (J1939 CAN on most Volvo/Renault/other HD trucks).
  • Code breakdown
    • MID 140: reporting ECU (cluster).
    • PSID 227: proprietary signal for the communication link to the APM/air dryer.
    • FMI 12: the target device is not responding properly (internal failure or datalink fault).
  • Why it happens
    • Wiring/connectors: The APM is chassis‑mounted and exposed to water/salt; green/white corrosion, pushed pins, and harness chafe are common.
    • Power/ground: A blown APM fuse, bad relay, or corroded ground stud will make the APM “silent,” which the cluster interprets as FMI 12.
    • CAN integrity: Open backbone/stub, missing/bad 120 Ω termination, shorted H/L, or a module dragging the bus.
    • APM failure: Internal electronics fault (water ingress, thermal cycling, aging).
  • Effects and symptoms you may see
    • Air dryer not purging or purging erratically; moisture in tanks; possible ABS/EBS secondary warnings if air quality/pressure control degrades.
    • Additional DTCs may appear in MID 185 (APM) if it is intermittently alive, or in other ECUs complaining about APM data timeout.

Current information and trends

  • Field experience on modern HD platforms shows the majority of FMI 12 communication faults at the APM trace to:
    • Connector corrosion and water‑wicking in harness splices.
    • Power/ground integrity issues after battery/relay/fuse‑box service.
    • Less frequently, outright APM controller failure.
  • Many current replacement APMs are plug‑and‑play, but OEM procedures may specify checks or parameter confirmations after install.

Supporting explanations and details

  • Quick electrical theory recap (J1939 CAN):
    • Two‑wire differential bus; quiescent ~2.5 V on both lines. Dominant bits: CAN‑H ≈ 3.5 V, CAN‑L ≈ 1.5 V (about 2 V differential).
    • Two 120 Ω terminators at bus ends → ~60 Ω measured between H and L with power off.
  • Expected measurements
    • Key off, battery disconnected: CAN‑H to CAN‑L ≈ 60 Ω (healthy), ≈120 Ω (one terminator missing/open), ≈0–5 Ω (short), OL (broken pair).
    • Key on: CAN‑H ≈ 2.5–3.5 V, CAN‑L ≈ 2.5–1.5 V (oscillating as messages pass). A steady 0 V/vehicle supply voltage indicates short to GND/B+.
    • APM supply: verify correct system voltage (12 V on most North American trucks; 24 V on some markets) at the APM power pin under load; voltage drop to APM ground <100 mV at 2–5 A load is a good target.

Ethical and legal aspects

  • Air system reliability is a safety‑critical function. Operating with an APM communication fault can compromise purge/drying, risking water carry‑over into brakes. In commercial operation, this can breach safety regulations and expose the operator to liability. If “STOP” or low‑air warnings occur, remove the vehicle from service until resolved.

Practical guidelines

  • Fast triage (10–20 minutes)
    1. Scan all ECUs. Note whether other modules also log APM data timeouts or general CAN faults. Record active vs. stored.
    2. Visual/physical: Locate the APM on the frame rail near the air dryer. Unplug, inspect both sides for moisture, green crust, bent/pushed pins; clean with contact cleaner, dry, reseat.
    3. Power/ground check at APM connector: confirm fused B+ and solid ground under wiggle/load.
  • Structured diagnostics
    • Step 1: Network health
    • With power off, measure CAN‑H to CAN‑L resistance at a convenient port (diagnostic connector or APM plug). Target ≈60 Ω.
    • If not ≈60 Ω, isolate: unplug modules one at a time (start with APM) until resistance normalizes; the last unplugged module/wiring branch is suspect.
    • Step 2: Shorts/opens
    • Check CAN‑H/L to chassis for low resistance (should be megaohms). If low, trace for pinch/chafe points along the frame and cab pass‑throughs.
    • Step 3: Power integrity
    • Backprobe APM B+ and ground with key on; load‑test the feed (headlamp bulb or electronic load) to catch high‑resistance faults that a DMM can miss.
    • Verify the APM fuse/relay and the ground stud condition (remove, clean to bare metal, treat, torque).
    • Step 4: Communication confirmation
    • With a J1939‑capable scan tool, check if the APM (MID 185) appears on the network and streams live data. If absent with good power/ground and healthy bus, the APM is likely failed.
  • Repair notes
    • If wiring/connector repairs are needed, use sealed butt splices or solder‑and‑adhesive heat‑shrink, maintain twist (≈1 turn per 25–30 mm) on CAN pair, and avoid stubs longer than OEM spec.
    • After replacing an APM, clear codes and verify purge cycles and water ejection. Some platforms require an ignition cycle or basic configuration check; follow OEM service info.

Possible disclaimers or additional notes

  • Some legacy or non‑Volvo/Renault implementations may map PSID 227 differently. For the common Volvo/Renault heavy‑duty context, PSID 227 at MID 140 points to APM communication. Earlier generic interpretations that tie this to “turbo/boost” or “general J1939 failure” are not applicable to this MID/PSID pairing.
  • Exact pinouts, fuse/relay IDs, and APM location vary by VIN and model year.

Suggestions for further research

  • Provide your truck make/model/year/VIN snippet so I can supply exact connector pinouts, fuse numbers, harness routing, and OEM test steps.
  • If intermittent: perform a datalog while performing a harness wiggle test around the frame rail and cab‑to‑chassis connector.
  • Consider a CAN bus analyzer to visualize bus errors (error frames, bus‑off events) if recurrent.

Brief summary

  • MID 140 PSID 227 FMI 12 = the cluster cannot communicate with the air dryer/APM; most often wiring/connector or power/ground to the APM, less often a failed APM.
  • Verify APM power/ground, inspect/repair the CAN wiring/terminations, and confirm network presence with a scan tool. Replace the APM only after these checks.
  • Share vehicle details and any additional symptoms, and I’ll tailor pinouts and a step‑by‑step for your specific platform.

User question

mid 128 sid 4 fmi 5

Artificial Intelligence Response

Direct answer to the question

  • Meaning: MID 128 SID 4 FMI 5 = Engine ECU (MID 128) has detected injector circuit fault on cylinder #4 (SID 4) with current below normal or an open circuit (FMI 5).
  • Key points:
    • This is an electrical fault in the injector #4 control circuit.
    • Most common causes: open injector coil, broken/chafed harness or poor connector contact, less often a failed ECU driver.

Detailed problem analysis

  • Code breakdown:
    • MID 128: Engine control module (ECM/EMS) on J1587/J1708/J1939.
    • SID 4: Component identifier for injector #4 on most heavy‑duty diesel ECUs using SIDs for unit/solenoid injectors.
    • FMI 5: “Current below normal or open circuit.” The ECU commanded the injector on but measured insufficient current, typical of an open coil or open/high‑resistance wiring.
  • Electrical theory of detection:
    • The ECU drives each injector via a high‑current power transistor (driver). It monitors driver current/voltage during the actuation window.
    • An open circuit (coil open, broken wire, or unseated connector) collapses current quickly; the ECU flags FMI 5 when the sampled current is below its learned threshold.
  • Typical root causes (in order of likelihood): 1) Injector #4 solenoid coil open (internal break). 2) Harness damage/open between ECU and injector (frequent at valve/rocker cover pass‑throughs and where the loom crosses brackets). 3) Connector issues (pushed pins, corrosion, water ingress) at the injector, under‑cover pass‑through, or ECU. 4) ECU driver failure (least common; confirm only after proving injector and wiring good).
  • Symptoms you may observe:
    • Dead miss on cylinder #4, rough idle, loss of power, possible white/black smoke, MIL/CEL on.
    • On aftertreatment engines, misfire can trigger secondary DPF/SCR efficiency or soot‑load related codes due to altered exhaust composition.

Current information and trends

  • Field patterns:
    • On Mack/Volvo MP-series engines, intermittent/open injector circuits often trace to breaks near the cylinder head harness pass‑through or specific loom legs (commonly noted by technicians as recurring failure points). Inspect these areas closely.
    • Many OEMs have TSBs/updated injector harnesses or pass‑through seals to address chafe and moisture ingress.
  • Diagnostic tooling trends:
    • Increasing use of guided diagnostics in OEM software to run cylinder cutout/buzz tests and to log driver current signatures, speeding isolation of coil vs. harness vs. ECU.

Supporting explanations and details

  • Expected electrical values (verify for your exact engine family):
    • Injector coil resistance, key‑off, at ~20–25°C:
    • Heavy‑duty diesel solenoid CR/EUI: typically 0.4–2.0 Ω (engine‑specific). “OL”/infinite = open coil.
    • Harness continuity (ECU pin to injector pin): typically <0.5 Ω end‑to‑end.
    • Short checks: Each injector lead to ground and lead‑to‑lead should read “OL” with connectors unplugged.
  • Control topology notes:
    • Many systems are battery‑feed to injector with ECU low‑side switching; others are high‑side drivers. Know which side is switched before testing so you don’t misinterpret readings.
  • Why a healthy engine can still set FMI 5:
    • Intermittent opens from vibration; thermal expansion at a cracked crimp; water in connector increasing contact resistance until it arcs/open circuits during high current.

Ethical and legal aspects

  • Safety:
    • Diesel injectors are actuated by high current and may coincide with high rail pressures. Do not back‑probe or scope injector circuits with the engine running unless you’re trained and using suitable probes and PPE.
  • Compliance:
    • Do not disable injectors or modify ECU strategies to mask the fault; this can violate emissions laws (e.g., U.S. EPA tampering prohibitions).

Practical guidelines

  • Step‑by‑step diagnostic plan (efficient and minimally invasive): 1) Confirm the fault:
    • Read and record all engine faults and freeze‑frame data. Note if MID 128 SID 4 FMI 5 is active or intermittent. 2) Visual inspection (5–10 min):
    • Inspect injector #4 connector for lock/latch, corrosion, spread terminals, oil/water wicking.
    • Trace harness from injector to head/rocker cover pass‑through, then to the main harness and ECU. Look for chafe points and tight bends. 3) Quick A/B isolation (“swap test”) if feasible:
    • Swap the electrical connectors between injector #4 and a known good cylinder (e.g., #5), or swap the injectors themselves if the platform allows and seals are on hand.
    • Clear codes and recheck:
      • Code follows the injector (now SID 5 FMI 5)? Injector #4 is faulty.
      • Code stays at SID 4? Suspect wiring/connector/ECU. 4) Static electrical tests (key‑off, battery disconnected; ECU and injector unplugged):
    • Coil resistance at injector #4: compare to OEM spec. OL/infinite = failed injector.
    • Continuity: ECU pin ↔ injector pin each lead (<0.5 Ω). Flex/wiggle harness while measuring for intermittent opens.
    • Shorts: Each lead to ground (OL) and lead‑to‑lead (OL). 5) Dynamic tests (if needed and trained):
    • Use OEM tool to run cylinder actuation/buzz tests and observe commanded vs. actual current. A flat/zero current trace on cyl #4 with others normal indicates open circuit. 6) Decide and repair:
    • If injector coil open → replace injector; follow cleanliness and torque/seal procedures; enter trim code if required.
    • If wiring fault → repair/replace harness section; use proper sealed splices, strain relief, abrasion sleeve; fix root‑cause chafe.
    • If connector issue → replace terminals/seals; correct pin tension.
    • Only after proving injector and harness good → evaluate ECU driver; proceed per OEM test plan and replacement policy.
  • Post‑repair verification:
    • Clear codes, perform warm idle and load test, confirm no misfire and no code return.
    • Inspect with thermal camera or IR thermometer after a road test; a cold cylinder can indicate a persistent injector issue.

Possible disclaimers or additional notes

  • SID mapping clarification: On engine MID 128, SID 4 is commonly injector #4. Some non‑engine modules use SIDs for different devices; avoid cross‑mapping with other MIDs. The boost/MAP sensor is typically identified by a PID (e.g., PID 102), not SID 4, in these systems.
  • Specifications vary by engine make/model/year and injector technology (solenoid vs. piezo). Always confirm exact ohmic values and procedures in the OEM manual.

Suggestions for further research

  • Provide engine make, model, year, and VIN if available. With that, I can return exact pinouts, connector part numbers/terminal IDs, resistance specs, and any OEM TSBs.
  • Useful areas to review in your OEM service information:
    • Injector harness routing/securing bulletin(s).
    • Pass‑through connector repair kits and crimp procedures.
    • ECU driver diagnostic flowchart for FMI 5 on your platform.

Brief summary

  • MID 128 SID 4 FMI 5 indicates an electrical open/low‑current fault on injector #4. Start with a visual and connector check, perform a swap test to isolate injector vs. harness, then measure coil resistance and harness continuity. Repair or replace the failed element (injector, wiring/connector), and only suspect the ECU driver after all other causes are excluded. If you share the exact engine, I’ll tailor specs and connector/pin guidance.

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