U1262 – SCP (J1850) Communication Bus Fault

Code | Fault Location | Probable Cause |
---|---|---|
U1262 | SCP (J1850) Communication Bus Fault (Buy Part On Amazon) | Power supply, Wiring, Fuses, Instrument cluster input sensors, PCM, GEM |
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Table of Contents
- What Does Code U1262 Mean?
- Where is the U1262 sensor located?
- What are the common causes of code U1262?
- What are the symptoms of code U1262?
- What are common solutions to code U1262?
- How serious is code U1262?
- How safe is it to still drive the car with code U1262?
- How difficult is it to repair code U1262?
- What are the common mistakes when repairing code U1262?
- How do you troubleshoot code U1262?
- Codes Related to U1262
- Get Help with U1262
What Does Code U1262 Mean?
OBD II fault code is a manufacturer specific code that is defined by car maker Ford as U1262 – “SCP (J1850) Communication Bus Fault”, or sometimes as “SCP (J1850) Communication Bus Fault – Instrument Cluster” and is set when the PCM (Powertrain Control Module) detects a communication failure between itself and HEC (Hybrid Electronic Cluster). Note that “SCP” in this definition means “Serial Communications Protocol”, which is Ford’s interpretation of the SAE (Society of Automotive Engineers) J1850 standard.
In simple terms, Serial Communication Protocol refers to the flow of data across a network that is more commonly referred to as a “bus”. In this case, the bus is the communication system across which the PCM delivers input data to all the instruments, warning lights, and other indicators on the instrument cluster. Typical information that flows across the bus involves vehicle speed, RPM (engine speed), engine/transmission temperatures, system voltages, and warning lights that indicate the status of various systems and features that may be fitted to the particular application.
The image below shows part of a typical Ford instrument cluster printed circuit. Note that apart from replacing this circuit board, it is generally not possible to repair Ford instrument clusters on a DIY basis.
Where is the U1262 sensor located?
The location of the instrument cluster is self-explanatory. However, the PCM on most Ford models is located under the hood on the left-hand side of the firewall (as seen from the driver’s seat), while the GEM (Generic Electronic Module) is usually located under the dashboard close to, or behind the radio.
What are the common causes of code U1262?
Some common causes of code U1262 could include the following-
- Interrupted or erratic power supply to the PCM
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
- Blown fuses or fusible links
- Defective or failed sensors that supply relevant input data to the instrument cluster via the PCM
- Failed or failing control modules that could include the PCM, and/or the GEM (Generic Electronic Module). Note though that control module failure is relatively rare, and the fault must be sought elsewhere before any control module is rare.
What are the symptoms of code U1262?
Some common symptoms of code U1262 could include the following-
- Stored trouble code and an illuminated warning light
- Several other codes may be present
- Depending on the exact nature of the problem, one or more(or all) warning lights may be illuminated permanently, or no warning lights may illuminate during self-test cycles
- Engine may crank without starting
- Instruments such as the fuel gauge may display incorrectly, erratically, or may not work at all
What are common solutions to code U1262?
The possible solutions to code U2162 are many and varied, and could include the inspection and repair/replacement of several of the components and systems listed below.
Mechanical:
- Engine oil filter
- Engine oil level
- Oil pump
- Engine oil level
- Oil pressure switch
- Engine coolant level
- Coolant thermostat
- Fuel gauge
- Collapsed or damaged fuel tank
- Fuel tank filler pipe/hose
- Indicated fuel level
- Fuel/EVAP lines
- Fuel tank filler cap
- Fuel filter (external to the fuel tank)
- Fuel tank
- Door, hood, and trunk adjustment
Electrical:
- Fuse(s)
- Bulb(s)
- LED(s)
- Wiring harness
- Electrical connector(s)
- Sensor(s)
- Instrument cluster
- Instrument cluster printed circuit
How serious is code U1262?
Code U1262 must be considered as serious, since functions such as engine/transmission coolant temperatures, and the fuel level may not be displayed correctly, if they are displayed at all.
How safe is it to still drive the car with code U1262?
Since the vehicle’s road speed may not be displayed accurately, it may not be safe to drive the vehicle while code U1262 remains unresolved.
How difficult is it to repair code U1262?
Non-professional mechanics should note that resolving this code can vary from moderately difficult, to extremely challenging, since in many cases, removal of the entire instrument cluster is required to gain access to the instrument cluster wiring connector.
Also note that tracing an open circuit in the bus system involves back-probing and testing every circuit that enters and leaves the instrument cluster. To do this successfully requires a repair manual that includes a wiring diagram, pin out charts, and reference data for that particular application. Also required is a good quality digital multimeter, as well as suitable back-probing adapters to avoid damaging electrical connectors.
Moreover, in most cases, “U” codes cannot be diagnosed accurately with cheap, generic code readers that cannot access communication bus systems. If suitable diagnostic equipment is not available, the better option is to refer the vehicle to the dealer or other competent repair facility for professional diagnosis and repair.
What are the common mistakes when repairing code U1262?
Instrument clusters and/or control modules, including PCM’s are often replaced in error (or desperation) when the fault is more likely to involve open circuits, damaged or short circuited wiring, defective relays, or blown fuses.
Note that control modules should never be replaced merely because a “U” code (module-to-module communications code) is present. These codes do not necessarily indicate a problem, since in some cases “U” codes can set as the result of normal self-test or diagnostic functions performed by the OBD II diagnostic system.
How do you troubleshoot code U1262?
Step 1
Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
NOTE: If other codes are present, note the order in which they were stored. Also determine their relationship with code U1262, and if any codes relate to the power supply of the PCM, investigate and resolve these codes before attempting a diagnosis of U1262. Failure to do this will result in a misdiagnosis and the distinct possibility that parts and components will be replaced unnecessarily.
Step 2
Once it is certain that the PCM’s power supply circuits are all in perfect working order, and that all related fuses and fusible links are intact, attempt to clear all codes to eliminate the possibility that this code was set as the result of normal diagnostic processes. If the codes clear and the vehicle can be driven, complete at least one complete drive cycle to see if any codes return.
NOTE: If blown fuses are found, do NOT replace them until the short circuit(s) or voltage overload(s) that caused them to blow have been found and repaired.
Step 3
If the fault persists, refer to the manual to determine the correct procedure to follow to remove the instrument cluster from the dashboard without breaking or damaging anything. Note that poor electrical connections in the instrument cluster connector is a common cause of code U1261, but the only way to gain access to the connector is to remove the cluster.
Step 4
Inspect the electrical connector, the instrument cluster, as well as the cluster printed circuit board for obvious signs or evidence of electrical or mechanical damage. Note that if the cluster itself shows signs of internal short circuits, the better option is to replace the cluster to ensure reliable operation of all instruments and indicators.
WARNING: Be aware that the instrument cluster is a programmable module, which means that the replacement cluster must be configured and integrated into the CAN bus system. Note that the required integration/configuration processes vary between models and trim levels, so refer to the manual to determine the correct procedure to follow to verify the success (or otherwise) of the process.
Step 5
Inspect the electrical connector for evidence of damage and/or corrosion. Pull the connector apart to inspect the pins/terminals in both halves, but resist the temptation to make repairs if pins are damaged or corroded. In these cases, the better option is to replace the connector or the relevant wiring harness to ensure proper operation of the cluster.
Step 6
Note that if the connector is undamaged, the diagnostic procedure becomes specific to the model from this point onwards.
Note that some indicators on the cluster have multiple inputs; for instance, the brake system warning light may receive input data from the brake fluid reservoir, the parking brake levers’ position switch, and in some cases, the brake light switch. In practice, this means that each circuit must be tested individually for resistance, ground integrity, and continuity.
NOTE: if the available code reader has control functions, initiate the diagnostic mode. This will test every circuit in the cluster, which saves a lot of time. However, on most, if not all models it is possible to initiate the self diagnostic mode manually without a code reader; refer to the manual to determine the appropriate steps on how to do this on the affected application.
Step 7
If the self-test mode reveals a problem, inspect the relevant circuit(s) for signs of damaged, shorted, disconnected, burnt, or corroded wiring and/or connectors between the cluster and the relevant control module. Make repairs or replace wiring as required if such damage is found.
Step 8
Note that if the self-test mode does not initiate or complete, it becomes necessary to test each circuit individually, in strict accordance with the instructions provided in the manual. Be aware though that this process can take many hours, and that great care MUST be taken during the entire process to avoid inadvertently causing short circuits that can damage wiring, components and/or control modules.
Test one circuit at time to avoid confusion and/or misdiagnoses. Compare all obtained readings with the values stated in the manual, and make repairs or replace wiring as required to ensure that all electrical values fall within the ranges specified by the manufacturer.
NOTE: To minimize the risk of damaging control modules, be sure to disconnect all wiring from the relevant control module(s) during resistance or continuity tests.
Step 9
If all electrical circuits check out but the fault persists, suspect either a defective instrument cluster or one or more failed control modules. Note though that it is far more likely far the cluster to have failed, so refer to the manual to determine the correct procedure to test the resistance/continuity of ALL testable circuits in the cluster.
Note that it is NOT advisable to attempt repairs of a Hybrid Electronic Cluster on a DIY basis. If testing reveals evidence of an internal failure of any part of the cluster, the better option is to replace the cluster, rather than attempting repairs that may or may not be effective.
Step 10
Once all repairs are complete, initiate the cluster self-test mode to verify the success of the repair. However, if the fault persists, refer the vehicle to the dealer or other competent repair facility for professional diagnosis and repair, since it may become necessary to test/replace either control modules, or large sections of the vehicles’ wiring.
Codes Related to U1262
There an known codes for Ford that are directly related to U1262 – “SCP (J1850) Communication Bus Fault – Instrument Cluster”
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ABS / Traction lights come on and go off intermittently. Also codes P1000 and U1262. I think I need the ABS module rebuilt.
Would you share the outcome with us? Seemingly the same issue here. I know it’s been a long time…
I have a draw on the battery and scanned codes p1000 & u1262 . My gauges seem to work ok just the odometer will go out sometimes and light back up . I’ve checked the gauge connections and the ecm connections and no corrosion. After all that I pulled the fuse to gauges and the ecm no change still had the draw. I pulled the gem module fuse and the test light went out . Would the problem be with the gem module then ?
It could be yes. But the gem module for a ford is kind of like a body control module. So there are more specific components you can check like the power windows, the instrument cluster, the radio, luggage compartment release switch, combination switch etc…. and unplug each one.ive seen trunks not closed all the way and the light stays on, but It seems like you are on the right track. Best of luck.
My 99 mustang 3.8L cranks but no start, has no spark, no fuel, dashes on the odometer and it stalled at a traffic light and wouldn’t start again. The anti theft system light is blinking rapidly also. Any ideas? Please I need some help with this.
Check the fuse box for a blown accessory fuse, then check power to the other fuses in the GEM. (Generic electronic module.) If these are okay, check the battery positive cable for crimps, fraying, or an exposed wire. If all these are okay, have your power and ground pins to the ignition wires to the pcm checked. I’m thinking it can be your PCM going bad. Best of luck.
I have my cluster going blank, and dashes instead of data. The speed needle remains at zero. The ABS, Trac, and Brake lights come on, the cruise control stops functioning. I have speed sensor(s) error codes and U1262.
When the car sits for at least 2 hours or overnight, the cluster works again, for a few minutes. It may function while driving for long periods of time after it has faulted.
When the cluster is working as expected, removing the ABS fuse creates the cluster fault, but when the fuse is put back in place, the cluster works fine (at least for a while). I visually inspected the ABS module (marked TCS) and could see it is clean and free of apparent corrosion. Harnesses seem OK. Cleaned connectors with a nylon brush as they did not show signs of corrosion.
Hypothesis 1 is a bad ABS sensor.
Hypothesis 2 is a bad ABS module or faulty wires.
Hypothesis 3 is a faulty cluster that does not receive the ABS data, and therefore send false faults.
Driving is normal when the cluster fails, braking remains unchanged, but the wheel is harder to steer.
I do not have a scanner allowing to display live speed sensors data, will be the car to shop for that avail.
Car should be drivable without ABS module, did not try yet. But if it is, this allows to send the module for rebuild for about $99 – as compared to $1,100 in order to get OEM part from the dealership – excludes labor/.
Any tips as to what direction to go now?
Hello Michael. My advice to you would be to hook it up to a decent scan tool and see if it can communicate with the abs module. It is pretty likely that the abs module might be shorting out intermittently. Bad modules can be somewhat difficult to diagnose when they give various symptoms such as these. Even deeper than the abs module, it could even be the ecm. But the abs module is most likely the problem. Best of luck.
Hello,
Any help / guidance with these codes 🙂 I think i will be crazy with them..
Scan Report Apr 10, 2021 09:20 PM
© BlueDriver 2019
2008 Mercury Grand Marquis
2MEFM75V78X611473
Odometer: 210,293 km
P0102 Mass or Volume Air Flow Sensor “A” Circuit Low
P0102 Mass or Volume Air Flow Sensor “A” Circuit Low
P0122 Throttle/Pedal Position Sensor/Switch “A” Circuit Low
P0223 Throttle/Pedal Position Sensor/Switch “B” Circuit High
P2104 Throttle Actuator Control System – Forced Idle
P2110 Throttle Actuator “A” Control System – Forced Limited RPM
U1262
STORED
(SCP) Data Link Fault
B1317
STORED
Third Row Power Fold Seat Output
B1208
STORED
Electronic Instrument Cluster Switch Bank Number 1 circuit short to ground
B1212
STORED
Electronic Instrument Cluster Switch Bank Number 2 circuit short to ground
U1900
STORED
Missing (Can) Message From The (Hec)
Page 1 of 3
1 Confirmed Code
5 Pending Codes
0 Permanent Codes
6 Instrument Panel Control Module / PATS Codes
© BlueDriver 2019
Scan Report – 2008 Mercury Grand Marquis
U2023
STORED
Fault Received from External Node
U0155
STORED
Lost Communication With Instrument Panel Cluster (IPC) Control Module
U2023
STORED
Fault Received from External Node
P0102 Mass or Volume Air Flow Sensor “A” Circuit Low
P0122 Throttle/Pedal Position Sensor/Switch “A” Circuit Low
P0223 Throttle/Pedal Position Sensor/Switch “B” Circuit High
P1000 On-Board Diagnostic (OBD) Systems Readiness Test Not Complete
P2104 Throttle Actuator Control System – Forced Idle
P2110 Throttle Actuator “A” Control System – Forced Limited RPM
U1041 Vehicle Speed Signal Missing Or Incorrect
U1059 Transmission Position Data Invalid
Page 2 of 3
1 Vehicle Dynamics Module / Suspension Code
1 Anti-Lock Brake Module Code
6 Powertrain Control Module Codes
2 Lighting Control Module Codes
3 Electronic Automatic Temperature Control Codes
© BlueDriver 2019
Scan Report – 2008 Mercury Grand Marquis
B1261 Sun load sensor short circuit to ground
U1341 Vehicle Speed Signal Missing Or Incorrect
U1073 Invalid Or Missing Data For Engine Coolant From (Pcm)
B2872 Tire Pressure Sensor Fault
B287A Tire Pressure System Fault
U1041 Vehicle Speed Signal Missing Or Incorrect
U1059 Transmission Position Data Invalid
Page 3 of 3
4 Drivers Door Module Codes
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Hello Hussain. This information is for the code U1262. In order for you to diagnose this you will have to check and look into a few things. In your fuse box, check to see if fuse 33 is missing, blown, or not making proper connection. The fuse goes to your fire supression system module. If the above mentioned is okay, check on the fire supression module under your passenger seat for a red with yellow wire on pin one. Check the resistance for proper ohms. On a schematic, the connector you’re looking for is C3281A. There should be about 60 ohms. Now, on pin 16, there is a wire pink with light green, and a wire that is white with light green. There proper resistance is around 60 ohms as well. If these are not within spec, then replace your fire supression system module. Good luck, and hope this helped.
Muy bien esplicado con muchos tisp grasias por su ayuda es una buena forma de trabajar contoda esta informacion