Codes 31, 33 And/Or 34: MAP Sensor

Some Eldorado and Seville models with DFI may exhibit poor performance at idle or deceleration. The "Service Now" light may also come on. This may be due to a rich running condition caused by a false MAP sensor input from Electromagnetic Interference (EMI). This EMI comes from 6 Meter Ham radio, TV or Navigation transmitters being conducted to the MAP sensor mounting bracket. Diagnose condition as follows:

1. Check for diagnostic trouble codes. Repair any codes other than 31, 33 and/or 34.
2. Remove lower passenger side dash panel and glove box. Using a digital ohmmeter, check for continuity between MAP sensor bracket and the instrument panel mounting bracket.
3. If there is no continuity, brackets are isolated and cannot cause condition. If there is continuity, the MAP sensor must be isolated.
4. Remove the MAP sensor. Discard the "C" clip. See "A" in Fig 1 . Apply 3 or 4 layers of duct tape to mounting brackets. See "B" in Fig 1 .
   Fig 1: Eldorado & Seville MAP Sensor

   
5. Punch a hole in duct tape and install MAP sensor with plastic fastener (1605396 ). Using a digital ohmmeter, ensure that no continuity is present between MAP sensor bracket and instrument panel mounting bracket.