Chart 10
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- Poor Fuel Economy
NOTE:
Driving styles may have a significant influence on fuel economy. Verify the concern before starting an in-depth diagnosis. Refer to the Owners Literature, Calculating Fuel Economy for additional information.
If available, use the integrated diagnostic system (IDS) fuel economy test to verify a concern is present. The following external factors may contribute to poor fuel economy:
- stop and go driving
- incorrect tire pressure and size
- vehicle loads (such as trailer towing)
- extended winter warm-up conditions
- high speed driving
- incorrect axle ratio
- road or weather conditions
- aftermarket add ons
- short run operations
- customer expectations
| SYSTEM/COMPONENT | REFERENCE (Engine Controls Pinpoint Test unless noted) |
|---|---|
Check the following PIDs:
|
LONGFT1 or LONGFT2 value low (-): Continue diagnosis. Concentrate checks in areas that would cause the engine to run rich. LONGFT1 or LONGFT2 value high (+): Continue diagnosis. Concentrate checks in areas that would cause the engine to run lean. VPWR not between 10.5 and 17.0 volts: REFER to the appropriate Charging System, Diagnosis And Testing article to continue diagnosis. VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage: CHECK the B+ voltage to the PCM power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK the PWR GND circuits. |
| Cooling System | Verify the engine operates at normal temperature. REFER to the appropriate Engine Cooling, Symptom Chart to diagnose any cooling system concerns that are present. |
| Transmission Fluid Level | Visual. |
| Secondary Ignition System | GO to Pinpoint Test JB. |
| Fuel Delivery System | GO to Pinpoint Test HC. |
| Exhaust System | GO to Pinpoint Test HF. |
| Variable Camshaft Timing (VCT) System | GO to Pinpoint Test HK. |
| Automatic Transmission | REFER to the Automatic Transmission, Diagnosis By Symptom article to continue diagnosis. |
| Positive Crankcase Ventilation (PCV) System | GO to Pinpoint Test HG. |
| Grille Shutter | REFER to the Front End Body Panels article, to continue diagnosis. |
| Additional Checks | Check for base engine or intake air system concerns. Check for a contaminated MAF sensor. REFER to the applicable Service Information article. Check for correct PCM VID block information. REfer to Flash Electrically Erasable Programmable Read Only Memory (EEPROM) to CARRY OUT the Making Changes To The VID Block procedure. |
| Auto Start Stop System | GO to Pinpoint Test AA. |
| Additional Testing | GO to Pinpoint Test Z. |