Yale 108-1 – Engine Control Unit (ECU): Barometric Pressure Below Acceptable Limit

The Barometric Pressure (BP) is estimated by the engine's TMAP or MAP sensor. The fault is triggered when the key is ON and the ECU detects that the barometric pressure reading has dropped below 8.30 psia. Because the BP value is critical for fuel and airflow calculations, this fault can cause starting issues or poor engine performance.

• Yale and Hyster Forklifts
• 2005 and newer Yale and Hyster forklifts
• Yale Veracitor VX series (GLP/GLC models)
• Hyster FT series
• Machines equipped with PSI 2.0L / 2.4L engines
• Machines equipped with GM, Mazda, and Yanmar engines

1. 1

   Verify if there is an open circuit on the 5-volt sensor supply line to the TMAP/MAP sensor

2. 2

   Inspect the signal circuit for an open wire or a short to the battery/sensor supply

3. 3

   Ensure the sensor ground circuit is not open

4. 4

   Using a diagnostic handset or software, check the live Barometric Pressure reading with the Key ON, Engine OFF. If it reads below 8.30 psia, the sensor or wiring is actively failing

5. 5

   Rule out a functional failure within the controller (ECU) itself

1. 1

   Visual Inspection

   Locate the TMAP/MAP sensor on the engine intake manifold. Inspect the sensor connector and wiring harness for chafing, corrosion, or backed-out pins.

2. 2

   Voltage Testing

   Disconnect the sensor. Turn the ignition key to the ON position (engine off). Use a multimeter to verify a steady 5V reference voltage and a solid ground at the connector.

3. 3

   Continuity Testing

   If the 5V reference or ground is missing, trace the wiring harness back to the ECU and repair any open or shorted wires.

4. 4

   Sensor Replacement

   If the wiring harness tests perfectly (good 5V supply, good ground, and continuous signal wire to the ECU), the TMAP/MAP sensor has failed internally and must be replaced.

5. 5

   Clear Codes

   Install the new sensor, reconnect the harness, and use the dash display or diagnostic tool to clear the fault codes. Cycle the key and verify the code does not return.