Engine Speed Sensor Signal Abnormal or Missing
What does PERKINS-190-8 mean?
The PERKINS-190-8 (Kohler RDC2) diesel fault code means: Engine Speed Sensor Signal Abnormal or Missing. This is a serious severity code.
Common Symptoms
- Generator cranks but will not fire and start
- Panel displays fault code 190-8 and red shutdown lamp is lit
- Generator shuts down immediately after attempting to start
- Engine cranks normally but RPM reading stays at zero on the controller display
- Weekly exercise cycle fails and unit logs a fault without starting
- PowerWizard 1.1 or 2.0 display shows 'Engine Speed Sensor Fault' or 'Speed Signal Abnormal'
- Unit enters lockout and will not attempt a restart without a manual fault clear
Probable Causes (Ranked by Likelihood)
- Crankshaft position sensor (magnetic pickup) has failed internally Very Likely
- Wiring harness to the crankshaft sensor is chafed, corroded, or has a broken pin at the ECM connector Very Likely
- Air gap between the sensor tip and the ring gear is out of specification (too wide or too narrow) Likely
- Ring gear teeth are damaged, cracked, or have significant debris buildup preventing a clean signal Likely
- ECM connector terminals are corroded or have moisture ingress causing intermittent signal loss Possible
- Engine ECM has lost calibration or has a software fault misreading a valid signal Less Likely
- Flywheel ring gear has slipped on the flywheel, shifting tooth timing relative to sensor position Less Likely
Step-by-Step Diagnostic Procedure
Step 1: Safety first. Switch the panel to OFF and disconnect the battery negative terminal before touching any sensor wiring. Perkins gensets store fault history in the ECM, so the code will still be there after you reconnect.
Step 2: Locate the crankshaft position sensor. On most Perkins 400, 1100, and 1300 series engines it threads into the bellhousing or timing case, close to the flywheel ring gear. It looks like a black cylindrical sensor about the size of your thumb with a two-wire or three-wire connector.
Step 3: Inspect the sensor connector visually. Look for green corrosion on the terminals, bent pins, or a broken connector latch that lets moisture in. If you see corrosion, clean with electrical contact cleaner and a small brush. If a pin is bent or broken, this connector must be repaired before going further.
Step 4: Check the sensor wiring from the connector back toward the ECM. Run your hand along the harness and look for spots where the insulation has rubbed through against the engine block or a bracket. Even a tiny nick can cause an intermittent open or short that triggers 190-8.
Step 5: With the battery reconnected, set your multimeter to AC millivolts. Unplug the sensor connector at the sensor end and measure resistance across the sensor's two signal terminals. A healthy Perkins magnetic pickup sensor typically reads between 200 and 1,000 ohms. A reading of zero (short) or open-loop (OL) means the sensor itself has failed and needs replacement.
Step 6: Check the air gap. With the sensor removed, thread it back in by hand until the tip just touches a ring gear tooth, then back it out one full turn. Reinstall the locknut. The target gap for most Perkins magnetic pickup sensors is 0.5 mm to 1.5 mm (roughly the thickness of a credit card to two credit cards stacked). If you cannot feel resistance when threading it in, the housing threads may be stripped.
Step 7: Inspect the ring gear teeth through the sensor port using a flashlight. Look for cracked, chipped, or heavily corroded teeth. If more than two adjacent teeth are damaged, the ring gear must be replaced before the sensor will produce a clean signal. This is an advanced repair requiring engine teardown.
Step 8: If wiring, sensor, and gap all check out, connect a laptop running Perkins EST (Electronic Service Tool) to read live engine speed data during cranking. If EST shows a speed signal during crank but the fault still sets, the ECM may need reprogramming or replacement. This step requires a dealer or certified technician with EST software access.
Frequently Asked Questions
What does Perkins code 190-8 mean?
Code 190-8 means the engine's crankshaft position sensor, sometimes called a magnetic pickup or speed sensor, is sending an abnormal signal or no signal at all to the ECM. The ECM needs this signal to know how fast the engine is spinning and to control fuel injection timing. Without it, the engine either will not start or shuts down immediately for safety.
Can my generator still run with this code?
No. A 190-8 fault will prevent the engine from starting or cause an immediate shutdown if it appears while running. The ECM treats a missing speed signal as a critical safety fault. You need to resolve the root cause before the generator will produce power again.
How much does it cost to fix?
If the sensor itself failed, you can buy a replacement Perkins crankshaft position sensor for $40 to $120 and swap it yourself in about 30 minutes. If a technician handles the full diagnosis and replacement, expect $150 to $400. If the wiring harness is damaged or the ECM needs reprogramming, costs rise to $500 or more.
Will the generator start the next time the power goes out?
Not while this fault is active. The controller locks out restart attempts after a 190-8 shutdown. Even if utility power fails, the genset will crank but not start. You need to fix the sensor or wiring fault and then clear the fault code from the PowerWizard display or using Perkins EST before the unit will respond to an ATS signal.