DTC 2-1-5 Valve Relay, Open Or Short Circuit

DESCRIPTION
Each time the control module is powered up when the ignition is switched on, it checks that the valve relay is working for about 1 second. If a fault occurs while driving, the system cuts out and the ABS warning light comes on. Once the system cuts out, the control signal to the hydraulic modulator, i.e. the signal to the valve relay, will be at about 12 volts, cutting out the valve relay and making the valve terminals dead.

CONDITIONS FOR DTC
If the signal to the valve relay is missing or short-circuited to the 12-volt supply or ground, the control module detects the fault and posts the DTC.

CONTROL VOLTAGE (hydraulic modulator, pin 2 - # 27)
A short-circuit to ground will be detected when testing the valve relay when the ignition is switched on. DTC 2-1-5 is posted. If a short-circuit to ground occurs while driving, this will not be detected until the next time the ignition is switched on, i.e. not while still driving. A short-circuit to +12 volt will be detected immediately and DTC 2-1-5 posted.

MONITORING SIGNAL (hydraulic modulator, pin 4 - # 32)
A short-circuit to ground is detected immediately and DTC 2-1-5 posted. If there is a short-circuit to +12 volts while driving, this will not be detected until the next time the ignition is switched on: in other words, a short-circuit to +12 V will not be detected once the valve relay has operated.

Symptoms

ABS warning light on, ABS system out of action.

Sources of fault

Faulty valve relay.

No power supply to pin 8 on hydraulic modulator contact.

No control voltage to pin 2 on hydraulic modulator connector: i.e. there is an open-circuit or short-circuit to 12 V or ground.

No monitoring signal to control module, i.e. open-circuit or short-circuit to hydraulic modulator connector pin 4.

ME1

Checking power supply to valve relay
- Ignition off.
- Connect a voltmeter between car ground (0 volts) and pin 8 on hydraulic modulator connector.
- Ignition on.
Voltmeter should read battery voltage (approx. 12 volts).
- Go to 'Checking control voltage', step ME3.

If reading is incorrect:

Cars with transient surge protection relay

If voltmeter reading is 0 volts this means there is an open-circuit in the lead between transient surge protection relay pin 2 and hydraulic modulator pin 8.

Cars with no transient surge protection relay

If voltmeter reading.is 0 volts, this means there is an open-circuit in the lead between the control module pin 17 and hydraulic modulator pin 8.

ME2

Checking lead between transient surge protection relay/ control module and hydraulic
modulator
- Ignition off.

Cars with transient surge protection relay
- Connect an ohmmeter between transient surge protection relay pin 2 and hydraulic modulator connector pin 8. If ohmmeter reading is around 0 ohms, lead is OK.

Go to ME3.

Ohmmeter reads infinite resistance: Open-circuit in lead.

Cars with no transient surge protection relay

- Connect test box between control module and ABS connector.

- Take reading across #17 and hydraulic modulator connector pin 8.
If ohmmeter reading is 0 ohms, lead is OK.

Go to ME3.

Ohmmeter reading is at infinity: Open-circuit in lead.


ME3

Checking for open-circuit in lead, control
voltage
- Ignition off.
- Connect test box between control module and ABS connector.
Connect an ohmmeter between #27 and hydraulic modulator connector pin 2.

Ohmmeter should read approx. 0 ohms.

If reading is correct:

Valve relay is faulty.
- Replace valve relay.

If reading is incorrect:

If ohmmeter reads infinite resistance, there is an open-circuit in the lead.

ME4

Checking monitoring signal

- Ignition off.
- Check ground points.
- Connect a voltmeter between ground (0 volts) and hydraulic modulator pin 4.
- Ignition on.
Voltmeter should read battery voltage (approx. 12 volts) when relay trips.

If reading is incorrect:

If voltmeter reads 0 volts, this means a faulty valve relay or an open-circuit in the lead between ABS connector pin 27 and hydraulic modulator connector pin 2 or short-circuit to ground.
- Go to ME5.

ME5

Checking monitoring signal (open-circuit)
- Ignition off.
- Connect test box between control module and ABS connector.
- Connect an ohmmeter between #32 and hydraulic modulator connector pin 4.
Ohmmeter should read 0 ohms.

If reading is correct:
- Deal with short-circuit.

If reading is incorrect:

If ohmmeter reads infinite resistance, this means there is an open-circuit in a lead somewhere.
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