Tachometer Inaccurate

Connect scan tool to Data Link Connector (DLC), and select ENGINE SPEED parameter. Start engine and warm up to operating temperature. Increase engine speed to 1500, 2000 and 3000 RPM. Compare scan tool readings to tachometer readings. If scan tool and tachometer readings are within 150 RPM or each other, tachometer is working normally. Inspect transmission for possible slipping problem. If readings are not as specified, replace tachometer.