Reviewers Note: Words/phrases in blue will be links to specific diagnostic procedures when this document is published in Freshdesk.

Blue iQ™ Fault Codes 7292 & 7293 Diagnostic Procedure

DSM.0029 Ver. 2.0 April 24, 2023
FC

SPN

FMI

Title

7292

8420

3

Fuel Storage Compartment 1 Temperature - Voltage below normal or shorted to a low
source - Most Severe Level

7293

8420

4

Fuel Storage Compartment 1 Temperature - Voltage above normal or shorted to a
high source - Most Severe Level

Parts Affected


Thermistor 1 – called “Fuel Storage Compartment Temperature Sensor 1” in Cummins INSITE™

Diagnostic Overview
The Blue iQ Fuel System Control Module (FSCM) monitors fuel cabinet(s) internal temperature by checking two
temperature sensors (thermistors) for any abnormal temperature values. When the FSCM detects sensor voltage
below normal, above normal, or shorted to a high source on one or more of the temperature sensors, it sets the
corresponding fault code.
In some cases, the FSCM also may send a signal to the Blue iQ™ Smart Gauge causing the indicator LED to
blink red and the gauge display to show a fuel system over temperature warning.
NOTICE Perform Initial Vehicle Check procedure prior to performing diagnostic instructions listed
below.

Diagnostic Links
Thermistor Circuit Diagram
Thermistor Resistance at Temperature Chart

Diagnostic Aids
During normal operation, the temperature inside the fuel system cabinet should not exceed 165°F; if the
temperature exceeds this value a warning screen on the Blue iQ™ Smart Gauge will notify the vehicle operator.

Circuit / Sensor Description
Thermistor 1 has a 5V Signal circuit and a Low Reference circuit which are provided from the FSCM. The signal
circuit in the FSCM monitors the 5V reference using a pull-up resistor; if there is an open circuit, the analog pin
will default to the peak 5V reading.
The Thermistor 1 Low Reference circuit is shared with Thermistor 2.
Refer to Thermistor Circuit Diagram for wiring details.

Circuit / System Verification
Step 1
Connect Cummins® INSITE™ to vehicle using J1939 OBD-II diagnostic interface and PC and navigate to “Agility®
Fuel Delivery System, CM1881 AFS(18)” module.

Reviewers Note: Words/phrases in blue will be links to specific diagnostic procedures when this document is published in Freshdesk.

Step 2
Record all active and stored fault codes and parameters prior to clearing fault codes using INSITE™.
Step 3
Observe and record Fuel Storage Compartment Temperature Sensor 1 data from INSITE™—is data within
reasonable operating range?
a. If not within range proceed to Circuit / System Testing.
b. If within range proceed to Step 4.
Step 4
Operate vehicle in the same conditions for enabling the fault code or within the same conditions that triggered
the fault code based on recorded data.
Step 5
Verify the fault code does not set. If any fault code sets proceed to Circuit / System Testing.
Step 6
While observing Fuel Storage Compartment Temperature Sensor 1 parameters in INSITE™ perform a wiggle
test on Thermistor 2 and FSCM connectors and harness to test for poor or intermittent connections.
a. If any fault code sets, proceed to Circuit / System Testing.
b. If no fault code sets, system is functioning to design intent.
Step 7
Review Circuit Diagram and FSCM and Thermistor Connector End Views to locate test points.

Circuit / System Testing
Step 1


Ignition OFF.



Disconnect Thermistor 1 from Blue iQ chassis harness.



Test for resistance across Terminal A and Terminal B of Thermistor 1 connector and record the value.



Use a non-contact infrared thermometer to measure temperature at Thermistor 1; record the value.



Use the Thermistor Resistance at Temperature Chart to determine whether the thermistor is operating
within design specifications.
Resistance value within specified range at measured temperature?
Yes – Proceed to Step 2.
No – Replace Thermistor 1.

Step 2


Ignition ON, Engine ON.



Test for 4.8-5.2 V between Thermistor 1 harness connector 5V Signal Cavity A and Low Reference Cavity
B.

Less than 4.8V? – Proceed to Step 3.
Between 4.8-5.2V? – Replace Thermistor 1.
Greater than 5.2V? – Proceed to Step 6.

Reviewers Note: Words/phrases in blue will be links to specific diagnostic procedures when this document is published in Freshdesk.

Step 3


Ignition ON, Engine ON.



Test for 4.8-5.2 V between Thermistor 1 harness connector 5V Signal Cavity A and a known good ground
such as the chassis frame rail.

Voltage between 4.8V and 5.2V?
Yes – Proceed to Step 7.
No – Proceed to Step 4.
Step 4


Ignition OFF.



Disconnect FSCM Blue iQ harness connector.



Test for infinite resistance between FSCM harness connector Cavity 13 and a known good ground.

Infinite resistance?
Yes – Repair 5V Signal circuit.
No – Proceed to Step 5.
Step 5


Ignition OFF.



Disconnect FSCM Blue iQ harness connector.



Test resistance between FSCM harness connector Cavity 13 to Thermistor 1 harness connector Cavity
A.

Resistance between 0 and 2 ohms?
Yes – Replace FSCM.
No – Repair 5V Signal circuit.
Step 6


Ignition OFF.



Disconnect FSCM Blue iQ harness connector.



Ignition ON.



Test for voltage between FSCM harness connector Cavity 13 and a known good ground.

Voltage between 0 and 1 V?
Yes – Replace FSCM.
No – Repair 5V Signal circuit.
Step 7


Ignition OFF.



Disconnect FSCM Blue iQ harness connector.



Test resistance between FSCM harness connector Cavity 28 to Thermistor 1 harness connector Cavity
B.
Yes – Replace FSCM.
No – Repair 5V Low Reference circuit.