Without Scan Tool

HOW TO DISPLAY AND READ DIAGNOSTIC TROUBLE CODES

Fig. 28 Diagnostic Code Index:

When the CHECK ENGINE warning light has been reported on, turn the ignition ON, pull down the passenger's side carpet inspection flap from under the dashboard, and monitor the LED on the top of the control unit. The LED indicates a system failure code by its blinking frequency.
The control unit LED can indicate any number of simultaneous component problems by blinking separate codes, one after another.
If codes other than those listed are indicated, count the number of blinks again. If the indicator is in fact blinking these codes, substitute a known good ECU and recheck. If the indication goes away, replace the original ECU.
The CHECK ENGINE warning light and control unit LED may come on, indicating a system problem, when in fact, there is a poor or intermittent electrical connection. First, check the electrical connections, clean or repair connections if necessary.