Join Date: Dec 2014
Location: Tucson, AZ
Posts: 1,524

U0100 - LOST COMMUNICATION WITH ECM/PCM
U0164 - LOST COMMUNICATION WITH HVAC CONTROL MODULE
U0155 - LOST COMMUNICATION WITH CLUSTER/CCN
(instrument cluster, Cab Compartment Node or BCM body control module)
U140B - IMPLAUSIBLE LEFT REAR WHEEL SPEED SIGNAL RECEIVED
U1409 - IMPLAUSIBLE LEFT FRONT WHEEL SPEED SIGNAL RECEIVED


As you have already determined there's lots of communications codes being logged and the wiring harness has issues. The main communications modules include the PCM, TCM and BCM/FCM.

PCM = powertrain control module
TCM = transmission control module
BCM = body control module
FCM = front control module


I don't know if the 2005 has a BCM or a FCM. The FCM is mounted on the front side of the engine bay fuse box. The BCM is mounted under the instrument panel (my 2012 has the BCM on the passenger side).


The CAN bus (Controller Area Network) is a twisted pair. CAN-B operates at a lower speed than CAN-C and provides communication among body and interior modules. CAN-C is for critical powertrain, anti-lock brake and electronic stability functions.


All nodes are connected to each other through a two wire bus. The wires are a twisted pair with a 120 Ω (nominal) impedance.The CAN bus must be terminated. The termination resistors are needed to suppress reflections as well as return the bus to its idle state. High speed CAN uses a 120 Ω resistor at each end of a linear bus. Low speed CAN uses resistors at each node. Signals across the bus are "0" and "1". Signaling drives the CAN high wire towards 5 V and the CAN low wire towards 0; with the differential voltage at a nominal 2 V.



The other wires on the CAN bus are power & ground. A typical CAN bus connector will have four wires or pins:

CAN-Low (CAN−)
GND (Ground)
CAN-High (CAN+)
CAN V+ (Power)

You can check the physical connections/wires but you need a CAN bus analyzer to see what messages are being transmitted over the CAN bus.

Join Date: Jan 2019
Location: Annapolis, IL

Mine has the module on the fuse box in front. I have found the twisted wires in the harness. I found a set of 4 twisted. Voltage wise, what should I see on the CAN V+? I am assuming ground is ground and I should be able to check it to the chassis. On the can data wires, should I be able to check at the PCM plug across those and read 120 ohms? Is that

disconnected or connected? I do have a PDF shop manual, but there are so many pages that I really don't even know where to start my search for tracking things out. I assume I can check the CAN V+ at each module? Do you by chance have any idea about what frequency the CAN C bus runs at?

From what I am reading here, it looks like this is pointing to a bad PCM or wiring. It seems there is quite some problems with that part. The HVAC is working (seemingly ok), gauges are working, trans responds to manual shifting or auto, although very abrupt. I did replace the wheel sensors on the left side, but didn't clear the codes. I just don't want to replace the

PCM only to have the exact same problems. I found the ground problems when cleaning and checking the connections. I am very inclined to run a new and specific ground from the battery to the engine block, then a good jumper from the engine to the strut tower.

Join Date: Dec 2014
Location: Tucson, AZ
Posts: 1,524

The only diagnostic procedures I have seen for CAN Bus issues has been the Network Diagnostics that are included with the advanced diagnostic systems (e.g. dealerships, collision centers, etc ...).
The PCM cannot determine a poor system ground so ensuring you have good system grounds is a good idea. Inspecting the PCM pins, connector/wiring is a good idea but probing the PCM pins or PCM harness connectors can damage the PCM circuitry ... so it's not recommended. The dealership attaches a Miller Special Tool #8815 (PCM pinout box) when they

need to measure/probe the signals.
https://www.ebay.com/itm/MILLER-SPEC...frcectupt=true