944 Turbo KLR Self-Diagnosis — Flash Codes

The KLR control unit on the 1985 944 Turbo is the knock and charging-pressure control unit (German Klopfregelung, hence "KLR"). It watches the knock-control and charging-pressure-control system, and when it detects a fault it stores it as a two-digit flashing code. Reading that code is the fastest way to point diagnosis at the right circuit — the knock sensor, the charging-pressure timing valve, the throttle-valve potentiometer, the pressure sensor, or the control unit itself.

This page covers the KLR self-diagnosis flash codes only. The same Test Plan also contains a full 15-test-point guided procedure (oscilloscope and voltmeter readings at each connector); that guided procedure is not reproduced here.

Reading the flash code

The fault memory is erased when the ignition is switched off, so the readout has to be done immediately after the fault has occurred.

1. Drive the car so the fault actually occurs. A code is only stored while the fault is present, and the memory clears the moment the ignition goes off.
2. Do the readout right after the test drive, without switching the ignition off. If you turn the key off first, the stored code is gone and you have to drive again to reproduce it.
3. Connect test adapter P 9246 — a testing relay with a built-in LED — into the test socket in the engine compartment, and watch the LED.
4. Read the two digits. The LED flashes the first digit, pauses, then flashes the second digit. Count each burst: N flashes, a pause, then M flashes gives the code "N–M". For example, three flashes, a pause, then one flash is code 3–1.

Caution: Because the memory is cancelled at ignition-off, plan the drive and the readout as one continuous operation — reproduce the fault, coast to a stop, and read the LED with the ignition still on.

Flash codes

Each stored fault has its own two-digit code. Find the code the LED gave you below, then work the possible cause and the check or remedy.

Flash code 1–2 — Battery voltage too low

Fault: battery voltage below 10.2 V.

Possible cause: the power supply — alternator, voltage regulator or battery.

Check: test the charging system and the battery, and correct whatever is holding the supply voltage down.

Flash code 2–1 — Knock sensor monitor

Fault: the knock-sensor monitoring circuit has flagged a problem.

Possible cause: the plug is loose, there is a wire break, or the sensor is faulty.

Check: test the knock sensor. Disconnect the KLR control-unit plug and connect an ohmmeter across terminals 11 and 13; the reading should be 270–330 kΩ. A reading of 0 Ω or infinite resistance points to the wiring or a failed sensor — check the wiring, and replace the sensor if the wiring is good. When refitting the sensor, tighten it to 11 N·m8 ft·lb and use the original screw without a washer.

Flash code 2–3 — Control unit faulty

Fault: the KLR control unit itself is faulty.

Remedy: replace the control unit.

Flash code 3–1 — Charging pressure too low

Fault: the charging (boost) pressure is too low.

First check the charging pressure. Connect pressure tester P 9103/2 to the pressure-damper vacuum connection and place it in the car. The test value is 0.70 bar10 psi at 3000 rpm at full load in 3rd gear. If the pressure is low, work through the possible causes:

• Timing-valve plug fallen off, wire break, or timing valve faulty → check the timing valve: (a) power supply — put a voltmeter on the red/green wire of the timing-valve plug to ground; it should read battery voltage. If it does not, follow the power-supply check (test point 2). (b) Coil resistance — pull the coil connector off the timing-valve plug and read across both connectors with an ohmmeter: 30 Ω. (c) Continuity — check the wire from KLR plug terminal 2 through to the timing valve. If all three check out, replace the KLR control unit.
• Vent line to the solenoid valve plugged → check it for free flow.
• Exhaust leak → check the exhaust for leaks.
• Leak in the intake → run the intake-system leak test (test point 14).
• No pressure on the bypass valve → check its activation and operation; the bypass valve must open under vacuum.
• Break in the pressure hose to the KLR control unit (no pressure display) → check the hose for flow and leaks.
• Charging-pressure control valve seized open → check the valve. The exhaust must be cold. Disconnect the pressure hose and connect pressure pump VAG 1274, then start the engine: the exhaust pipe leading to the control valve must heat up shortly, and the pipe leading away from it must stay cold (valve closed). Now supply 0.6 bar9 psi to the control valve — the pipe leading away must now heat up (valve open).
• Turbocharger faulty → check the turbocharger.
• Exhaust "closed" (catalytic converter blocked) → connect pressure tester P 9103/2 to the exhaust test pipe; the test value at 3500 rpm at full load is 0.8 ± 0.1 bar1 psi for 0.7 bar10 psi charging pressure.
• Throttle valve does not open fully → adjust the throttle linkage if applicable.

Flash code 3–2 — Charging pressure too high

Fault: the charging (boost) pressure is too high.

Main cause — the timing valve always has electric current. Check the timing valve: (a) power supply as above; (b) coil resistance 30 Ω as above; (c) pull the plug on the timing valve, connect a test lamp across the plug contacts and switch the ignition on — the test lamp must not come on. If all three check out, replace the KLR control unit.

Other possible causes:

• Break in the line to the timing valve or to the charging-pressure control valve → check the line for flow and leaks.
• Timing-valve inlet (orifice) plugged → check it for free flow.
• Charging-pressure control valve seized closed, or diaphragm leaking → check the control valve (exhaust cold; the VAG 1274 pressure-pump procedure from code 3–1).

Flash code 3–3 — Pressure sensor faulty

Fault: the pressure sensor is faulty.

Remedy: replace the KLR control unit.

Flash code 4–1 — Throttle-valve potentiometer

Fault: the throttle-valve potentiometer circuit.

Possible causes: the power-supply wire to the potentiometer is grounded out, the plug has fallen off, or the potentiometer is faulty → run the throttle-switch / potentiometer test (test point 9).

Note: This code can also appear for a 3–3 case where the pressure sensor is in fact good.

Flash code 4–2 — Throttle-valve potentiometer

Fault: the throttle-valve potentiometer circuit.

Possible causes: a break in the wire to the potentiometer, or the potentiometer is faulty → run the throttle-switch / potentiometer test (test point 9).

Related

• 944 Turbo (951) FAQ — how the turbocharger and charging-pressure control system work, and how the KLR drives the cycling (timing) valve.
• DME Diagnosis — the Motronic DME side of engine management, which works alongside the KLR on the 944 Turbo.
• 944 Exhaust System — Layout, Flanges & Torques — the exhaust path a blocked "closed" exhaust (code 3–1) sits in.