U0100 on 2008-2020 Dodge Grand Caravan: Lost Communication With ECM/PCM Causes and Fixes

What's Unique About the 2008-2020 Dodge Grand Caravan

On this generation of Dodge Grand Caravan, many communication issues that set a U0100 code are not caused by the PCM itself, but by the Totally Integrated Power Module (TIPM). The TIPM acts as the central gateway and fuse box, and it's a known weak point that can cause symptoms identical to PCM failure, such as stalling or a no-start condition. 🎬 Watch: Diagnosing a no-start caused by PCM communication loss. It's critical to differentiate between a faulty TIPM and a faulty PCM to avoid replacing the wrong expensive component. Another common failure point specific to this platform is the wiring harness chafing against the body in the driver's side wheel well, causing a short that cuts power to the PCM.

Generation note: The 2008-2020 year range covers the entire fifth generation (RT) of the Dodge Grand Caravan. While the core architecture is the same, there were updates to modules and wiring over the years. Notably, a recall (U87 / NHTSA 18V-332) for a faulty voltage regulator chip in the PCM affected 2017-2018 models, which could cause stalling or a no-start condition. Another recall (U49 / NHTSA 18V-332) addressed a software issue where cruise control might not disengage if the CAN bus failed, requiring a PCM software update for 2014-2018 models.

Symptoms You May Notice

• Engine will not start or has a no-crank condition.
• Intermittent or sudden stalling while driving.
• Check Engine Light is on.
• Multiple warning lights on the dashboard may illuminate simultaneously, sometimes called 'Christmas treeing'.
• Gauges on the instrument cluster stop working or behave erratically.
• The red dot security light on the instrument cluster may stay on or flash, and the radio may ask for an anti-theft code.
• Reduced engine power and poor fuel economy.
• Erratic behavior from electrical components like the radiator fan, wipers, or interior lights, often linked to a failing TIPM.

Most Likely Causes

1. Faulty Totally Integrated Power Module (TIPM) 🔴 High Probability → Shop Fuse Box The TIPM on this platform is a notorious failure point and acts as a central communication hub. Internal relay or circuit board failures are common and can cut off communication to the PCM, cause fuel pump issues, or other electrical gremlins.
   How to confirm: A professional scan tool can check for communication with the TIPM and see if it's commanding power to the PCM. Swapping the ASD and other relays can be a diagnostic step. Some owners use a 'TIPM bypass cable' for the fuel pump relay as a temporary fix or diagnostic tool.
   Typical fix: Replacement of the TIPM. Some companies like Circuit Board Medics and MAKS TIPM Rebuilders offer repair services for specific internal faults. A used TIPM may cause security lock-out issues.
   Est. part cost: $300-$800
2. Damaged or Corroded Wiring Harness 🟡 Medium Probability Wiring harnesses, particularly the main harness routed through the driver's side front wheel well, are exposed to moisture and vibration. It is very common for wires to chafe against a body stud or other components, leading to a short circuit that cuts power or communication to the PCM. Corrosion in connectors under the TIPM is also frequent.
   How to confirm: Visually inspect the wiring harness leading to the PCM (located in the driver's side wheel well area) and under the TIPM for any signs of chafing, green corrosion, or broken wires. Check for continuity on the CAN bus wires (typically White/Orange and White) and power/ground wires to the PCM.
   Typical fix: Repair the damaged section of the wiring harness or replace the affected connector. This often involves splicing in a new section of wire and protecting it from future damage.
   Est. part cost: $20-$200
3. Low Battery Voltage or Poor Connections 🟡 Medium Probability → Shop Vehicle Battery Modern vehicle modules are sensitive to voltage. A weak battery (below 12.4V) can cause unpredictable communication dropouts between modules, triggering a U0100 code as a first symptom.
   How to confirm: Test the battery with a multimeter; it should read at least 12.6 volts with the engine off. Load testing the battery is a more definitive test. Clean and tighten battery terminals and check the main ground connections to the chassis and engine block.
   Typical fix: Recharge or replace the battery. Clean or replace battery terminals and ground straps.
   Est. part cost: $150-$300
4. Faulty Powertrain Control Module (PCM) ⚪ Low Probability → Shop Engine Control Module (ECM) While less common than TIPM or wiring issues, the PCM can fail internally. A recall (U87 / NHTSA 18V-332) was issued for a faulty voltage regulator chip in the PCM on 2017-2018 models that could cause this code and a no-start or stall.
   How to confirm: This is typically the last part to suspect. If the battery, wiring, grounds, and TIPM all check out, and there is confirmed power and ground going to the PCM but no communication coming out (verified at the PCM connector), the PCM is likely faulty.
   Typical fix: Replace the PCM. This requires programming the new module with the vehicle's VIN and configuration data.
   Est. part cost: $500-$1200

Rare But Worth Checking

• Faulty CAN Bus Terminating Resistor: The CAN bus network has terminating resistors (often 120 ohms each, located inside modules like the PCM and TIPM) to prevent signal reflections. The total network resistance measured between CAN High and CAN Low should be ~60 ohms. If a module containing a resistor fails, it can disrupt the entire network.
• Aftermarket Electronics: Improperly installed aftermarket accessories like remote starters, alarms, or even radios can interfere with the CAN bus network by tapping into the wrong wires or introducing electrical noise, causing communication errors.
• Faulty Wireless Ignition Node (WIN) Module: In some cases, a failing WIN module (the part that reads the key fob) can cause anti-theft system lockouts and communication issues on the CAN bus, leading to a no-start and sometimes a U0100 code.

Diagnosis Steps

1. Check Battery Health: Ensure the battery is fully charged (12.6V+) and that terminals are clean and tight. Load test the battery to be certain.
2. Scan for All Codes: Use a capable OBD-II scanner to pull codes from all vehicle modules (ABS, BCM/TIPM, Airbag, etc.), not just the engine. Note all 'U' (communication) codes present.
3. Inspect Fuses and Relays: Check all fuses related to the PCM, TCM, and TIPM. Swap the ASD (Auto Shutdown) relay with a known good relay (like the horn or A/C relay) to see if the condition changes.
4. Visual Wiring Inspection: This is a critical step. Remove the driver's side front wheel and fender liner. Thoroughly inspect the wiring harnesses connected to the PCM and running along the frame. Look for chafed wires, especially where the harness may rub a body stud, corrosion on connectors, or rodent damage. Also inspect the connectors under the TIPM.
5. Check Power and Grounds at the PCM: Using a wiring diagram for your specific year, verify that the PCM is receiving proper battery voltage on all its power pins and has solid ground connections at its ground pins. A user on 2CarPros detailed checking for 12.4V at pins 80 and 96 and ground at pins 49, 50, 51, 52, 53, and 72 of connector C1 on a 2014 model.
6. Test the CAN Bus Network: This is an advanced step. With the battery disconnected, use a multimeter to check resistance between Pin 6 (CAN-H) and Pin 14 (CAN-L) at the OBD-II port. A healthy network should read approximately 60 ohms. If it's 120 ohms, a terminating module is offline. If it's near 0 ohms, the wires are shorted together.
7. Diagnose the TIPM: If power and grounds to the PCM are good but communication is still lost, the TIPM becomes a primary suspect. A professional may need to test its outputs, or you may consider a known-good used unit for testing, though this can sometimes trigger security issues.

Parts You'll Likely Need

• Totally Integrated Power Module (TIPM)

Related Codes That Often Appear With This One

• U0101 — Lost Communication with TCM. On the Grand Caravan, the TCM (Transmission Control Module) is integrated into the PCM. If the PCM fails or loses power, communication is lost with both, triggering U0100 and U0101.
• U0140 — Lost Communication With Body Control Module. The TIPM often serves as the Body Control Module (BCM). A failing TIPM can trigger both U0140 and U0100 simultaneously.
• P0688 — ASD Relay Sense Circuit Open/High. This code often appears with U0100 if the TIPM fails to properly power up the Auto Shutdown (ASD) relay, which in turn powers the PCM and other critical engine components. A P0688 strongly points towards a power supply issue to the PCM, either from the TIPM or wiring.

Technical Service Bulletins (TSBs) & Recalls

• Recall U87 - Powertrain Control Module Voltage Regulator
• Bulletin #08-068-16: This manufacturer update notes that U0100-00 (Lost Communication With ECM/PCM) should be performed to reduce the potential for misdiagnosis of related systems and incorrect module replacement.

Platform-Specific Known Issues

• Recall U87 / NHTSA 18V-332: Affects some 2017-2018 Grand Caravans. The Powertrain Control Module (PCM) may have a faulty voltage regulator chip that can fail, causing a stall or no-start condition and setting a U0100 code. The fix is to replace the PCM.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: 120 Ohms indicates a terminating resistor/module is offline. ~0 Ohms indicates CAN High and CAN Low wires are shorted together.
• CAN Bus Voltage (Key On) — expected: CAN High and CAN Low should both read approximately 2.5V.. Failure: Abnormal voltage readings can indicate a short or open in the CAN wiring or a faulty module pulling the voltage down.
• PCM Power Supply Voltage at Connector C1 (2014 model example) — expected: Battery voltage (~12.4V+) at pins 80 and 96 with key on.. Failure: 0 volts indicates a loss of power from the TIPM or an open/short in the harness.
• PCM Ground Circuit Resistance at Connector C1 (2014 model example) — expected: Less than 1.0 Ohm between ground pins (49, 50, 51, 52, 53, 72) and a known good chassis ground.. Failure: High resistance indicates a poor ground connection, which can cause unpredictable module behavior and communication faults.
• ASD Relay Sense Circuit Voltage (P0688) — expected: Battery voltage should be present at the PCM sense pin when the ASD relay is commanded on.. Failure: No voltage sensed at the PCM when the relay is energized will set code P0688, indicating a problem with the relay, its fuse, or the wiring.

Scan Tool Commands That Help

• WiTech / WiTech 2: Restore Vehicle Configuration — This function is used after replacing a PCM, especially with a used unit. It writes the vehicle's original VIN and configuration data into the replacement module, which is essential for it to communicate with other modules on the network.
• WiTech / WiTech 2: PCM Replaced — This is a specific function within the immobilizer (WIN/SKIM) module menu. After installing a new or used PCM, this procedure is required to transfer the secret security key, allowing the new PCM to be accepted by the anti-theft system so the engine can start.
• High-end bidirectional scanner: Actuator Tests / TIPM Relay Activation — To diagnose a suspect TIPM, a technician can command specific relays (like the ASD or fuel pump relay) to turn on and off directly from the scan tool. If the relay clicks and provides output voltage, it confirms the TIPM is receiving the command and the relay is functional, pointing the diagnosis elsewhere.

Wiring & Ground Locations

• PCM Location — Inside the driver's side front wheel well, behind the fender liner.. This location exposes the PCM and its wiring harness to moisture, salt, and physical damage from road debris. The harness is known to chafe against a body stud in this area, causing shorts that cut power or CAN communication.
• G300 — At the base of the driver's side 'B' pillar.. This is a major chassis ground point for multiple interior modules. While not a direct PCM ground, a poor connection here can introduce electrical noise and cause communication issues across the vehicle network.
• G301 — At the base of the passenger's side 'B' pillar.. Similar to G300, this is a key chassis ground point. A loose or corroded G301 can cause seemingly unrelated electrical issues that may disrupt network stability.
• Engine Mount Ground Strap — Connects the engine block (near the upper passenger side engine mount) to the chassis.. This is a primary ground path for the engine and its components, including the alternator. A broken or corroded strap can cause unstable voltage and grounding for the PCM and other sensors, leading to communication errors.
• PCM Connectors (C1, C2, C3, C4) — Plugging into the PCM module in the driver's side wheel well.. These are the direct interface for all power, ground, and communication lines to the PCM. Testing for voltage, ground, and CAN signals must be done at these connectors to confirm if the fault is with the PCM itself or the wiring leading to it.

Real Owner Repair Stories

• 2CarPros Forum User (2014 Dodge Grand Caravan) — No-charge condition, battery draining.
  ❌ Tried (didn't work) Replaced battery., Bench-tested original alternator (it passed)., Replaced alternator with a new one., Installed two different pre-programmed used PCMs, which caused other problems., Had a used PCM reprogrammed by the dealer, which fixed some but not all issues.
  ✅ What actually fixed it The owner eventually installed a new Mopar PCM from the dealer and had it programmed, which finally resolved the charging issue. This highlights that even after verifying wiring, the PCM itself can be the ultimate point of failure, and that used/reman PCMs can be unreliable.
• NHTSA ODI #11331197 — An owner reported that every single time the vehicle died while driving or failed to start while parked, a U0100 engine code was present.
• NHTSA ODI #11153349 — A report describes a vehicle experiencing communication errors including U0100 and U0101 related to the communication to the TCM and PCM.

OEM Part Supersession History

• 56049720 (series) → Varies by letter revision (e.g., 56049720AT) — Internal component and software updates to address reliability issues.
  Heads up: TIPMs for 2008-2010 models are generally not compatible with 2011+ models due to significant wiring and feature changes.
• 04692335 (series) → 68244893 (series) — Revisions to internal relays and circuit board design.
  Heads up: These TIPMs are specific to the early Pentastar engine years and may not work with later models that have different features.
• 68239606 (series) → Varies by letter revision (e.g., 68239606AA) — Ongoing software and hardware revisions.
  Heads up: Specific to later model years. Using an earlier TIPM (e.g., from a 2012) in a 2018 van will result in feature loss and communication errors.

Model Year Variations Within This Range

• 2008-2010: These models used the 3.3L, 3.8L, and 4.0L V6 engines. Their TIPM and PCM architecture is distinct from the later Pentastar-equipped vans. Part numbers for these modules are not interchangeable with 2011+ models.
• 2011-2020: All models from 2011 onward use the 3.6L Pentastar V6. While the engine is consistent, the TIPM and PCM part numbers changed several times. A major TIPM change occurred around 2014/2015, so it is critical to match part numbers exactly when replacing.
• 2017-2018: These specific years were subject to a PCM recall (NHTSA 18V-332) for a faulty internal voltage regulator that could cause stalling and a U0100 code. Any diagnosis on these years should begin by checking if this recall was performed.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• 3.6L Pentastar Rocker Arm/Camshaft Failure 🔴 High — Common, especially on earlier models (pre-2016), but can occur at any mileage, often starting after 75,000 miles. Presents as an engine 'ticking' noise. (Ref: Multiple TSBs have been issued over the years. A class-action lawsuit was filed regarding this issue.)
• 62TE Automatic Transmission Problems 🔴 High → Shop Transmission Assembly — Common. Issues include harsh shifting, shuddering, slipping between gears, or stalling when coming to a stop. Solenoid pack failure is a frequent cause. (Ref: Numerous TSBs exist for various transmission symptoms and software updates.)
• Cracked/Leaking Oil Filter Housing 🟠 Medium — Very common on the 3.6L Pentastar engine. The plastic housing can crack from heat cycles and over-tightening, causing significant oil leaks onto the engine block.
• Premature Brake Wear 🟠 Medium — Widespread on earlier 5th-gen models (approx. 2008-2012). Owners report replacing pads and rotors much more frequently than expected due to undersized components for the vehicle's weight. (Ref: A recall was issued for some early models to address brake issues.)
• Underbody Coolant Leaks from Rear HVAC Lines 🟡 Low — Common on models equipped with rear heat/AC. The aluminum lines running to the rear of the vehicle are prone to corrosion and leaking.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used PCM or TIPM from a junkyard can be a cost-effective option IF you can verify the donor vehicle did not have electrical issues and the part number is an exact match. It is a gamble, as internal electronic faults are not visible.

Donor-vehicle mileage cap: roughly under 120000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Check for an exact part number match, including the final two letters (e.g., '68239606AA').
• Inspect all connector pins on the module for corrosion, discoloration, or physical damage.
• Ask for the VIN of the donor vehicle to check for any outstanding recalls related to the module.
• Avoid modules from vehicles with signs of flood damage or major front-end collisions.

OEM-only on this vehicle (don't cheap out):

• Powertrain Control Module (PCM): While used PCMs can work, they often require dealer programming. Given the high failure rate of aftermarket/reman units reported in forums, a new OEM part, despite the cost, offers the highest chance of a one-time fix.

Aftermarket brands forum-validated for this vehicle:

• Circuit Board Medics (Repair Service): Well-regarded for repairing original TIPMs, which avoids programming issues.
• MAKS TIPM Rebuilders (Repair/Reman): Another company with positive reviews for rebuilding and selling remanufactured TIPMs.
• Dorman (Remanufactured): A common aftermarket option for TIPMs. Quality can be inconsistent, but they are widely available and often come with a warranty. They are generally considered remanufactured OEM units.

Brands owners have reported issues with on this vehicle:

• Unbranded/No-Name eBay PCMs: Many forum stories report issues with cheap, pre-programmed PCMs from unknown online sellers, often leading to more diagnostic headaches.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• U1197 — A communication code that frequently appears alongside U0100 during no-crank/no-start diagnostics on the 2012 Grand Caravan.
• U0101 — Often accompanies U0100 when the TIPM (the central communication hub) fails, affecting multiple modules simultaneously.
• P0688 — Related to the ASD (Auto Shutdown) relay sense circuit; the ASD relay is a primary component to check when diagnosing U0100 no-start conditions.
• B1234 — Body-related codes may surface when the TIPM experiences internal circuit board failure, affecting interior lights and wipers alongside PCM communication.

Frequently Asked Questions