'85-'89 PGM-FI
'88-'90 PGM-CARB

'90-'91 PGM-FI
Clearing ECU codes
For a description and explanation of what the sensors are see the glossary!

ECU Error Codes

3rd generation ECU error codes and ECU location. To access the codes (if any) turn the ignition key to the on position but do not start the car. Locate the indicator LED and count the number of flashes. Single digit codes are indicated by a series of short flashes. Two digit codes use a long flash for the first digit followed by the appropriate number of short flashes. After a short pause the the code will repeat. For multiple codes the codes will flash alternately with a pause between codes.
ie. For code 3 and 14....
The LED will flash 3 times, pause, flash once long then 4 times, pause and repeat from the beginning.

On '85-'87 Preludes the ECU is located in the left side trim panel beside the rear seat. On '88-'91 Preludes the ECU is located under the carpet on the right passenger floorboard.

'85-'89 PGM-FI

Code 0 ECU
Code 1 Oxygen content A
Code 2 Oxygen content B
Code 3 MAP sensor
Code 4 Crank angle sensor
Code 5 MAP sensor
Code 6 Coolant temperature
Code 7 TPS sensor
Code 8 TDC position sensor
Code 9 No.1 cylinder position sensor
Code 10 Intake air temperature sensor
Code11  
Code 12 Exhaust gas recirculation system
Code 13 Atmospheric pressure sensor
Code 14 Electronic idle control
Code 15 Ignition output signal
Code 16 Fuel injector
Code 17 Vehicle speed sensor

'88-'90 PGM-CARB

Code 1 Oxygen content
Code 2 Vehicle speed pulser
Code 3 MAP sensor, electrical signal
Code 4 Vacuum switch signal
Code 5 MAP sensor, vacuum signal
Code 6 Coolant temperature
Code 7 Clutch switch signal (manual trans.)
Code 7 Shift position signal (auto trans.)
Code 8 Ignition coil signal
Code 9 Intake air temperature
Code 10 Electronic Air Control Valve (EACV)


'90-'91 PGM-FI

Code 0 ECU
Code 1 Oxygen content A *, Oxygen content **
Code 2 Oxygen Content B
Code 3 MAP sensor
Code 4 Crank angle sensor
Code 5 MAP sensor
Code 6 Coolant temperature
Code 7 Throttle position sensor
Code 8 TDC position sensor
Code 9 No.1 cylinder position sensor
Code 10 Intake air temperature sensor
Code11  
Code 12 Exhaust gas recirculation system
Code 13 Atmospheric pressure sensor
Code 14 Electronic air control
Code 15 Ignition output signal
Code 16 Fuel injector
Code 17 Vehicle speed sensor
Code 41 ** Oxygen sensor heater
Code 43 ** Fuel supply system

* 2.0 liter engines
** 2.1 liter engines

Clearing ECU codes

Stored codes are earased from memory by disconnecting power to the ECU for at least 30 seconds. Disconnecting the negative battery cable will clear the memory of the ECU, as well as other solid-state equipment such as radios. The ECU may also be cleared by pulling the appropriate fuse from the underhood fuse and relay box. This may be the BACK-UP, CLOCK or CLOCK/RADIO fuse.

 

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