SPN 103 - FMI 18 (Fault Code 687)

SPN103 FMI18 (Turbocharger 1 Speed - Data Valid But Below Normal Operating Range)
Fault Code 687
ISB, ISC, and ISL with CM2150 - Turbocharger 1 Speed Circuit

Fault Code: 687
PID(P), SID(S): P103
SPN: 103
FMI: 1/18

REASON: Turbocharger 1 Speed - Data Valid But Below Normal Operating Range - Moderately Severe Level. Low turbocharger speed detected by the ECM.

EFFECT: Engine power derate. The ECM uses an estimated turbocharger speed. To clear the
fault code after a repair, take the vehicle on a short test drive with a few hard accelerations
from stop to approximately 35 mph.

Circuit Description:
The turbocharger speed sensor is a variable reluctance speed sensor. It consists of a coil of wire and an iron core. The target on the turbocharger shaft is a ground flat in the center of the shaft. As the flat on the turbocharger shaft spins past the speed sensor, a signal is generated. The electronic control module (ECM) interprets this signal and converts it to a turbocharger speed reading.

Component Location:
The turbocharger speed sensor is mounted in the center housing of the turbocharger.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The ECM detects that the turbocharger speed is detected to be less than 600 rpm for more than 1 second when the engine speed is greater than 1200 rpm.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• The ECM will estimate turbocharger speed.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes. To clear the fault code after a repair, take the vehicle on a short test drive with a few hard accelerations from stop to approximately 35 mph.

Shop Talk:
Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

This fault can possibly come active if the ECM senses engine speed while at the same time a turbocharger speed signal is less than 600 rpm.

Possible causes of this fault code include:
• Damaged turbocharger speed sensor
• Damaged engine harness
• Damaged alternator (EMI or internal short)
• Damaged ECM.

This fault becomes inactive any time the speed signal from the turbocharger speed sensor returns.
If the fault occurs intermittently, look for causes of intermittent open or short circuits in the turbocharger speed sensor circuit (including the speed sensor pigtail connector).

For the code to clear, the ratio of boost pressure to ambient pressure must be above 1.19:1 for at least 30 consecutive seconds. This condition can only be achieved during a test drive when the engine is under load. Operating the engine at idle or high idle while stationary will not create enough load to maintain boost pressure at 1.19 times ambient pressure for 30 consecutive seconds.

Although it is possible for a damaged ECM to be the root cause of this fault code, it is highly unlikely and ECM replacement should only be considered as a last resort if no other repairs are successful in clearing the fault code.

In very rare cases, it has been shown that the turbocharger can cause this fault code to come active and turbocharger replacement may be the only way to clear the fault code.

Read More:
SPN 103 - FMI 2 (Fault Code 686)
SPN 167 - FMI 1 (Fault Code 598)


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1 Response to "SPN 103 - FMI 18 (Fault Code 687)"

  1. Hello. Read the information on this page, then replaced a new (but no longer working) sensor with my old but guaranteed working sensor. And it immediately burned out and displayed the same error. Please tell me, what could it be? Why did the sensor burn out instantly? Thank you very much and have a nice day.