Posted on by

Electronic Control System Gas Plus Engines – FAULT CODE 2191

Mixer Inlet Pressure, Intake Manifold Pressure, and Exhaust Back Pressure Do Not Agree

Overview

CODE REASON EFFECT
Fault Code: 2191
PID: P102
SPN: 102
FMI: 11/31
LAMP: Amber
SRT: 

Manifold Absolute Pressure Sensor disagrees with the Mixer Inlet Pressure Sensor or the Exhaust Back Pressure Sensor.

Possible reduced performance.

Atmospheric Pressure Sensors
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) uses these three sensors to validate the atmospheric pressure.

Component Location

The mixer inlet pressure sensor is located in the air inlet elbow, the intake manifold pressure/temperature sensor is located in the intake manifold, and the exhaust back pressure sensor is connected to the exhaust.

Shop Talk

Atmospheric pressure is used to calculate base fueling to the engine.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Read the fault codes. Fault Code 2191 active?
STEP 2. Check the sensor’s pressure readings.  
  STEP 2A. Check the pressure readings of the mixer inlet pressure sensor, intake manifold pressure sensor, and exhaust back pressure sensor. Pressure for all three sensors is approximately 96.53 kPa [14 psia] or 723.90 mm Hg [28.5 in Hg] (atmospheric pressure)
STEP 3. Clear the fault codes.  
  STEP 3A. Disable the fault code. Fault Code 2191 inactive?
  STEP 3B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Read the fault codes.

Conditions

  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

Read the fault codes.

Fault Code 2191 active?
YES NO
No Repair No Repair

Guided Step 2 – Check the sensor’s pressure readings.

Guided Step 2A – Check the pressure readings of the mixer inlet pressure sensor, intake manifold pressure sensor, and exhaust back pressure sensor.

Conditions

  • Turn keyswitch ON
  • Do not start the engine.

Action

  • Turn the keyswitch ON, but do not start the engine.
  • Use INSITE™ electronic service tool to check the mixer inlet pressure, intake manifold pressure, and exhaust back pressure.

Pressure for all three sensors is approximately 96.53 kPa [14 psia] or 723.90 mm Hg [28.5 in Hg] (atmospheric pressure)?
YES NO
No Repair

One or more pressures do not meet specification. Troubleshoot appropriate sensor circuit.

  • Troubleshoot the mixer inlet pressure sensor circuit. Go to Fault Codes 122 and 123.
  • Troubleshoot the intake manifold pressure sensor circuit. Go to Fault Codes 354 and 355.
  • Troubleshoot the exhaust back pressure sensor circuit. Go to Fault Codes 591 and 592.

Appropriate fault code(s)

Guided Step 3 – Clear the fault codes.

Guided Step 3A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

  • Start the engine and let it idle for one minute.
  • Verify that Fault Code 2191 is inactive.

Fault Code 2191 inactive?
YES NO
No Repair

Troubleshoot procedures need to be repeated from the beginning.

Guided Step 3B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON.

Action

  • Use INSITE™ electronic service tool to erase the inactive fault codes.

All fault codes cleared?
YES NO
No Repair

Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting charts
Last Modified:  17-Aug-2004
Avatar photo

Published by Jack

Hello, I'm Jack, a diesel engine fan and a blogger. I write about how to fix and improve diesel engines, from cars to trucks to generators. I also review the newest models and innovations in the diesel market. If you are interested in learning more about diesel engines, check out my blog and leave your feedback.