Fault in the instrument panel cluster itself, such as internal failure or poor internal connections; Damaged, corroded or loose wiring or connectors on the serial data circuit between the cluster and the control module; Low battery voltage, poor battery connections or a weak charging system causing modules to drop off the network; Missing power or ground supply to the instrument cluster, for example a blown fuse or a corroded ground point; Fault on the data network caused by another module or aftermarket device pulling the bus down; Fault in the control module that is reading the data, or outdated software in the cluster or control module (model and year dependent).

P1604

Loss Of IPC Serial Data.

Cadillac
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
6: AreaComputer and output circuits
04: FaultThe specific fault in that area

What it means

On a Cadillac, P1604 means Loss Of IPC Serial Data. The engine control module (or another module that listens for instrument panel cluster messages) stopped receiving the expected serial data from the instrument panel cluster (IPC) on the vehicle communication network. The fault is stored when that communication is missing or unreliable, so the cause may lie in the cluster, the wiring, the network or the module's power and ground supplies.

Symptoms

Instrument cluster gauges dead, stuck or behaving erratically
Warning lights on the dashboard, such as the check engine light or other warning lamps
Speedometer, tachometer or fuel gauge not working
Other communication fault codes stored in several modules
Intermittent no-start or poor starting if security or immobiliser messages pass through the cluster
Driver information messages missing or incorrect

Possible causes

Fault in the instrument panel cluster itself, such as internal failure or poor internal connectionslikely
Damaged, corroded or loose wiring or connectors on the serial data circuit between the cluster and the control modulelikely
Low battery voltage, poor battery connections or a weak charging system causing modules to drop off the networkpossible
Missing power or ground supply to the instrument cluster, for example a blown fuse or a corroded ground pointpossible
Fault on the data network caused by another module or aftermarket device pulling the bus downpossible
Fault in the control module that is reading the data, or outdated software in the cluster or control module (model and year dependent)rare

How to diagnose

Read all stored codes from every module and record freeze frame data, noting whether other communication codes or cluster codes are present
Check the battery condition and charging voltage, and make sure battery terminals and main earths are clean and tight
Check the fuses and relays that supply the instrument cluster and compare against the wiring diagram for your model and year
Inspect the cluster connector and the serial data wiring for damage, water ingress, corrosion, chafing or previous repairs
Check whether the cluster powers up, runs its self-test and communicates with the scan tool; note if it is missing from the module list
Test the cluster's power and ground supplies, and test the serial data circuit for continuity, short to ground and short to voltage using the manufacturer's wiring diagram
Disconnect any aftermarket accessories connected to the data network and see whether communication returns
Check for any applicable software updates or service information for your model and engine, as procedures vary

How to fix

Repair or replace damaged wiring, connectors or terminals on the serial data circuit
Restore the cluster's power and ground supplies, replacing blown fuses only after finding why they failed
Repair or replace the battery or charging system if low voltage is upsetting network communication
Repair or replace the instrument panel cluster if it is confirmed faulty, and carry out any setup or programming it needs
Remove or correct any faulty aftermarket device that disturbs the network
Update the control module or cluster software only where an outdated calibration is a known cause for your vehicle

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but you should have it checked soon because the gauges and warnings you rely on may not be working. If the car stalls, will not start reliably or the speedometer and warning lights are dead, limit driving until it is fixed.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.